Cowboys loved a colorful phrase! This was a variation of "stuck up." Uppish meant proud or insolent.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 7 words with the pattern U--IS-. That is, six letter words with 1st letter U and 4th letter I and 5th letter S. In alphabetical order, they are:

unkiss

unwise

unwish

unwist

uppish

uprise

uprist

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern UPP--H. That is, six letter words with 1st letter U and 2nd letter P and 3rd letter P and 6th letter H. In alphabetical order, they are:

uppish

It could be used, yes and would be understandable. Here are some more synonys: assumptive, arrogant, cavalier, chesty, haughty, highfalutin (also hifalutin), high-and-mighty, high-handed, high-hat, huffish, huffy, imperious, important, lofty, lordly, masterful, overweening, peremptory, pompous, presuming, presumptuous, pretentious, self-asserting, self-assertive, sniffy, stiff-necked, supercilious, superior, toplofty (alsotoploftical), uppish, uppity.