When something looks suspicious or doubtful
When he was talking about how big was his penis, I began to smell a rat...
When a woman touches her inner labia and then smells her fingers to see how fresh she smells. The name is derived from that fact that the texture of the inner labia is similar to that of some fish used in sushi.
I caught Tina with her fingers down her pants... I thought she was fingering herself but it turns out she was just smelling the sushi.
When something (i.e. a room, clothes, your mom) smells exceptionally bad, as definined by the usual smells of a persons rectum.
A derogatory nickname for the Pepsi-owned fast food chain, Taco Bell; inspired by the repulsive, cheese-like scent of the fungus (Candida albicans) which flourishes under the foreskin of an unkempt, uncircumcised penis (and in the vagina of women with yeast infections).
Fuck that, I'm not eating at Cockmold Smell - I'd rather fuck your Canesten-using mom.
When you cut a large one, the expression one may use to ask if anyone else notices it.
"Frank struck gold in his pants, anyone else smell that jazz?"
Inhaling second hand smoke while having a conversation with someone who is smoking while not actually smoking yourself.
Person One: "I'm going to go smoke a cigarette."
Person Two: "I've got to talk to you, I'll go outside and smell a cigarette with you."
Or
Person One: "Dave's outside smelling a cigarette with the landlord."
Popular, one-on-one childrens game in which one player lies on his back and pulls his knees to his chest, while his opponent gets on his knees and smells his butt. The object is to quit as soon as your butt gets smelled, and/or before you have to smell a butt.
"Hey Mikey, you wanna play smell butts? OK, you go first"