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1.
a Slang word for something derived from simply the word something just with a u as the o and no g giving you sumthin; has the same meaning as something but easyier to spell
In an AIM or MSN messager conversation

"Yo dude you gotta come over & see what I got"
"what is it?"
"SUMTHIN! It's awesome just come over and check it out dude."
by Jer-Hey! June 20, 2008