1. To fit snugly onto something, creating an audible snap when doing so. All these pieces just snap onto the main body, so you can customize your toy robot to look whatever way you want. The webcam snaps onto the top of the monitor, making video calls much more manageable.

2. To cause or force something to attach snugly onto something else, creating an audible snap when doing so. In this usage, a noun or pronoun can be used between "snap" and "onto." I just need to snap these wings onto the fuselage and then my model airplane will be finished! The soldier snapped the scope onto the rifle and aimed it at his target.