1
general::
Put on or hold a social gathering, as in They're throwing a party to introduce their nephew to the neighbors, or She threw a party every Saturday night. [Colloquial; first half of 1900s]
American Heritage Idioms
2
general::
Phrase(s): throw a party (for someone)
Fig. to have a party; to hold a party; to arrange a party. • Bill threw a party for his sister before she went away to college. • Things seem sort of dull. Let’s throw a party.
McGrawhill's American Idioms And Phrasal Verbs