Phrasal verb is a phrase (such as take off or look down on) that combines a verb with a preposition or adverb or both and that functions as a verb whose meaning is different from the combined meanings of the individual words. (source: merriam-webster)
A phrasal verb consists of a verb and a preposition or adverb that modifies or changes the meaning; ‘give up’ is a phrasal verb that means ‘stop doing’ something, which is very different from ‘give’. The word or words that modify a verb in this manner can also go under the name particle.
Phrasal verbs can be divided into groups:
Intransitive verbs
These don’t take an object They had an argument, but they’ve made up now.
Inseparable verbs
The object must come after the particle.
They are looking after their grandchildren.
Separable verbs
With some separable verbs, the object must come between the verb and the particle:
The quality of their work sets them apart from their rivals. .
In English a phrasal verb is the combining of two or three words from different grammatical categories — a verb and a particle, such as an adverb or a preposition — to form a single semantic unit on a lexical or syntactic level. Examples: turn down, run into. There are tens of thousands of them, and they are in everyday, constant use. These semantic units cannot be understood based upon the meanings of the individual parts but must be taken as a whole. In other words, the meaning is non-compositional and thus unpredictable.
There are at least three main types of phrasal verb constructions depending on whether the verb combines with a preposition, a particle, or both. The phrasal verb constructions in the following examples are in bold.
When the element is a preposition, it is the head of a full prepositional phrase and the phrasal verb is thus prepositional. These phrasal verbs can also be thought of as transitive and non-separable; the complement follows the phrasal verb.
a. Who is looking after the kids? – after is a preposition that introduces the prepositional phrase after the kids.
b. They picked on nobody. – on is a preposition that introduces the prepositional phrase on nobody.
c. I ran into an old friend. – into is a preposition that introduces the prepositional phrase into an old friend.
d. She takes after her mother. – after is a preposition that introduces the prepositional phrase after her mother.
e. Sam passes for a linguist. – for is a preposition that introduces the prepositional phrase for a linguist.
f. You should stand by your friend. – by is a preposition that introduces the prepositional phrase by your friend.
When the element is a particle, it cannot (or no longer) be construed as a preposition, but rather is a particle because it does not take a complement. These verbs can be transitive or intransitive. If they are transitive, they are separable.
a. They brought that up twice. – up is a particle, not a preposition.
b. You should think it over. – over is a particle, not a preposition.
c. Why does he always dress down? – down is a particle, not a preposition.
d. You should not give in so quickly. – in is a particle, not a preposition.
e. Where do they want to hang out? – out is a particle, not a preposition.
f. She handed it in. – in is a particle, not a preposition.
Many phrasal verbs combine a particle and a preposition. Just as for prepositional verbs, particle-prepositional verbs are not separable.
a. Who can put up with that? – up is a particle and with is a preposition.
b. She is looking forward to a rest. – forward is a particle and to is a preposition.
c. The other tanks were bearing down on my Panther. – down is a particle and on is a preposition.
d. They were really teeing off on me. – off is a particle and on is a preposition.
e. We loaded up on snacks. – up is a particle and on is a preposition
f. Walter has been sitting in for me. – in is a particle and for is a preposition.
Note that prepositions and adverbs can have a literal meaning that is spatial or orientational. Many English verbs interact with a preposition or an adverb to yield a meaning that can be readily understood from the constituent elements.
He walked across the square.
She opened the shutters and looked outside.
These more readily understandable combinations are not phrasal verbs, although some books and dictionaries may include them in lists of phrasal verbs.
Furthermore, the same words that occur as a genuine phrasal verb can also appear in other contexts, as in
1(a) She looked up his address. Phrasal verb.
1(b) She looked his address up. Phrasal verb.
2(a) When he heard the crash, he looked up. Not a phrasal verb.
2(b) When he heard the crash, he looked up at the sky. Not a phrasal verb.
An extension of the concept of phrasal verb is that of phrasal noun, where a verb + particle complex is nominalized. The particles may come before or after the verb.
standby: We are keeping the old equipment on standby, in case of emergency.
back-up: Neil can provide technical backup if you need it.
onset: The match was halted by the onset of rain.
input: Try to come to the meeting – we’d value your input.
References:
Huddleston, Rodney; Quirk, Randolph; Greenbaum, Sidney; Leech, Geoffrey; Svartvik, Jan (June 1988). “A Comprehensive Grammar of the English Language”. Language. 64 (2): 345. doi:10.2307/415437. ISSN 0097-8507. JSTOR 415437.
Declerck, R. Comprehensive Descriptive Grammar of English, A – 1991 Page 45 “The term multi-word verb can be used as a cover term for phrasal verbs, prepositional verbs, prepositional phrasal verbs and combinations like put an end to.”
Other references and a bunch of phrasal verbs and their meanings can be found in the presentation below:
The Lectures 