Secret Internet Shorty, an acronym used to describe pictures of a guys dick but using angles or photoshop to make appear significantly bigger than it really is.
by IamIwhoIam August 20, 2011
Get the SISmug. 
An unbelievably rich cunt (richer than Bill Gates) who wears a monacle and probably has other characteristics but none you really care about.
Also likes boys and sniffing the sweatline under fat guys flabbing man breasts.
Also likes boys and sniffing the sweatline under fat guys flabbing man breasts.
Brian has loads of money for beer tonight. He could do a Si and buy the pub free drininks all night.
by Bobby Charlton March 18, 2004
Get the Simug. Due to the vast majority of lies which happens every time a person types 'LOL' in texting or the internet, SIS (Smile in Silence) is a much more proper use in times when one does not actually laugh when typing 'LOL'. Though, this may suggest that the person is not as fun as he did not actually laugh.
A: Yo, B, I just tried walking thru at a drive thru.
B: LOL, what happened?
A: B, stop lying bro, don't tell me you actually laughed at that message. SIS
B: Jeez, such a stickler...So what happened?
A: They told me that they only viewed car owners as acceptable customers.
B: SIS
B: LOL, what happened?
A: B, stop lying bro, don't tell me you actually laughed at that message. SIS
B: Jeez, such a stickler...So what happened?
A: They told me that they only viewed car owners as acceptable customers.
B: SIS
by Shinigami Prophet July 10, 2014
Get the SISmug. sexual intercourse sex hanky panky hot hottie awesome cool sexy 1. a word and hand-sign created to refer to sexual intercourse in a way unknown to rejects, spazes, and especially older, uncool adults, so your conversations remain esoteric.
2. this term can take the place of words such as hot, hottie, sexy lady, ect.
3. SI can also replace cool, awesome, ect.
2. this term can take the place of words such as hot, hottie, sexy lady, ect.
3. SI can also replace cool, awesome, ect.
ex1: Things are really going well with my gf. I think SI is an inevitability.
ex2: Whoa! Check her out! SI at 10 o'clock.
ex3: "Hey, there having free food at the party, and there's no addmission price this time!"
"Really? Aw, SI man!"
ex2: Whoa! Check her out! SI at 10 o'clock.
ex3: "Hey, there having free food at the party, and there's no addmission price this time!"
"Really? Aw, SI man!"
by Oddjob 007 September 28, 2006
Get the SImug. by Johnny Skeets September 18, 2005
Get the SImug. by kezza January 30, 2005
Get the simug.