I'm not an English major, but this does seem to exist as a word: http://dictionary.reference.com/browse/nonsemantic
Although it would mean "not pertaining to semantics", where "unsemantic" is usually used as "describing inaccurate semantic", so I'm not sure if it works 1:1
Anyway, just wanted to be a dick, feel free to close :)
I'm not an English major, but this does seem to exist as a word: http://dictionary.reference.com/browse/nonsemantic Although it would mean "not pertaining to semantics", where "unsemantic" is usually used as "describing inaccurate semantic", so I'm not sure if it works 1:1
Anyway, just wanted to be a dick, feel free to close :)