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 Verb:
lock someone or something up (somewhere)
Meaning:
to lock someone or something within something or some place.
Example:
The captain ordered the sailor locked up in the brig until the ship got into port.
A phrase 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