1
general::
Phrase(s): a kick in the (seat of the) pants [and] a kick in the ass; a kick in the butt; a kick in the teeth
Fig. Inf. a strong message of encouragement or demand. (Use ass and butt with discretion.) • All he needs is a kick in the seat of the pants to get him going. • A kick in the butt will get her moving.
McGrawhill's American Idioms And Phrasal Verbs