there is only one correct definition of pitch when referring to chains. it's not opinion or semantics, those who refer to 1/8" and 3/32" widths as pitch are just wrong.
from sheldon brown's glossary entry on pitch:
Pitch
The pitch of a chain is the distance between adjacent drive rollers. All modern bicycles use 1/2" pitch. Some older chains, especially those used on track bicycles used 1" pitch chain (see skip link and block chain.) For a while, Shimano experimented with a 10 mm pitch for track use, but it never caught on.
Sometimes people mistakenly refer to "track pitch" vs. "road pitch" when they are really referring to the wider (1/8") sprockets used on single-speed bicycles, instead of the 3/32" thick sprockets used on derailer-equipped bicycles.