1. To expel saliva or phlegm from one's mouth onto someone or something. I really wish you wouldn't spit onto the ground like that—it's really gross! Two troublesome youths sat on the overpass, spitting onto the people walking below.

2. To eject or expel an object from one's mouth onto someone or something. In this usage, a noun or pronoun is used between "spit" and "onto." Someone spat their gum onto the sidewalk, and it got stuck to the bottom of my sneaker! Make sure you don't talk with your mouth full—you don't want to spit food onto your date!