Definition of inch:
a unit of length
equal to one-twelfth of a foot
and equivalent to exactly 2.54 centimetre
s; the amount of water which would cover a surface to the depth of an inch, used as a measurement of rainfall
"Don't move an inch!"
(intransitive, followed by a preposition) To move
(in a particular direction)
"fearful of falling, he inched along the window ledge."