toggle
toggle: vt. To change a bit from whatever state it is in to the
other state; to change from 1 to 0 or from 0 to 1. This comes from
`toggle switches', such as standard light switches, though the
word `toggle' actually refers to the mechanism that keeps the
switch in the position to which it is flipped rather than to the
fact that the switch has two positions. There are four things you
can do to a bit: set it (force it to be 1), clear (or zero) it,
leave it alone, or toggle it. (Mathematically, one would say that
there are four distinct boolean-valued functions of one boolean
argument, but saying that is much less fun than talking about
toggling bits.)