A stand-up guy is someone whom you can trust; a trustworthy person; a reliable person who keeps other people's secrets.
Hooman is such a stand-up guy. Everyone in the class confides in him. His lips are sealed and you can't get a word out of him.
by rashouri October 1, 2013
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Mafia term A good solid man business man. not one to bullshit, can be trusted. Will do anything needed for his family.
AL: Should I worry that donnI is going to jack me on this deal?

Mikey: Donnie is a stand up guy, I trust him with my life.
by icedoutgear.com Dave April 6, 2006
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Meaning

A loyal and reliable friend.

Origin

The allusion is to someone who would be prepared to stand up and fight on your side if called on, i.e. one who, in the words of the earlier (late 19th century) phrase, would 'stand up and be counted'.

The phrase is American. The earliest citation is in the Pennsylvania newspaper The Charleroi Mail, April 1935:
"But he seems to be a stand up guy and loyalty, with him, seems to be less a virtue than obsession."
by Dixon St. Grottlesex. November 5, 2009
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trustworthy fella you can count on in any predicament
Oh course James Bridges can be counted on if you are in a bind. After all, he IS a stand up guy.
by F0ShizzleNizzle December 15, 2010
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Someone who won't give up anything under interrogation.
Standing up to questioning.
Cop: Awright asshole, where'd you get that illegal substance?
Guy: I dunno what that is or how it got there. Never seen it before.
Cop: Oh yeah? We're gonna lock up up and throw away the key if you don't tell us where you got that stuff.
Guy: I don't know NOTHIN' about it!

Dig it, you are a stand up guy!
by Straight Shooter October 1, 2007
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Michael Franzese
Hey man! Have you heard of Michael Franzese?

Are you kidding? He’s the definition of a stand up guy!

Oh, my bad!
It’s ok. Fuggetaboutit!
by Gonzorino September 9, 2020
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*John sees quadriplegic commit good deed*
John: Hey bud, you're a real stand-up guy!
Quadriplegic: ...
by eyyyy guy November 16, 2010
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