1. vt. To add a new element to a specified list, esp. at the top. “OK, cons picking a replacement for the console TTY onto the agenda.”
2. cons up: vt. To synthesize from smaller pieces: “to cons up an example”.
In LISP itself, cons is the most fundamental operation for building structures. It takes any two objects and returns a dot-pair or two-branched tree with one object hanging from each branch. Because the result of a cons is an object, it can be used to build binary trees of any shape and complexity. Hackers think of it as a sort of universal constructor, and that is where the jargon meanings spring from.