In music, a stab is a single staccato chord that adds dramatic impact to a composition. Stabs are usually provided by horns (real or synthesized), thus the term horn stab, or an orchestral sample, usually occur on a 1-beat, and are frequently used in funk, freestyle, and ska.
There's a rule of thumb in funk music that says short sounds are better than long: thus the drier the guitar hit, the tighter the horn stab, the slappier the bass, the more clipped the clavinet etc, the better. It's the bits of silence in-between these short events that builds anticipation for the next one - the tension/release principle in rhythmic form.—Steve Lodder[1]
As well, stabs are used in electronic music, in the form of tiny snippets of a song used as rhythmic accents in a new composition. Early Breakbeat Hardcore, such as Prodigy's Fire, and Hip hop in general made use of stabs.