It was actually on the "Simple English" Wikipedia I just realized. First paragraph:http://en.wikipedia.org/wiki/Logic_gate
Didn't jump out at me, but I only did a cursory search of the article. Mostly they referred to gates as Boolean functions.
Thing is, there are analog parts called comparators. They compare two DC voltages and output a 1 or a 0 depending. They are a single bit A/D converter.
The language is precise for a reason, it is a very deep subject.
"Logic gates compare the state at their inputs (source) to decide what the state at their output should be."
http://simple.wikipedia.org/wiki/Logic_gate