Phrasal verbs, also called two-word verbs, are idiomatic expressions wherein the second element of the verb (the adverb or particle) is not necessarily predictable.
Phrasal verbs are multi-word verbs that, like single-word verbs, convey action of the body or mind or occurrences. Phrasal verbs consist of a basic verb + another word or words, usually a preposition or adverb. Example: speak (basic verb) + up (preposition)