To work really hard on something.

A way of expressing that someone is sexually attractive. It is often used with irony or playfulness.

Comes from the verb “breed” which is to copulate with intent of bearing children.

For someone to be truly “breedable” they need to be fertile.

To bust ass is to fart. BUT if used with a possesive, it means to work hard.
Also often used with a possessive and immediately followed by an infinitive

when somebody lets out a disgustingly huge fart; this is usually announced.

To fall real hard on ones ass.

to rip an unprecdentedly large fart, one that sounds like a large plane has just flown overhead

also see busting ass

past tense: busted ass

A woman whose breast cleavage looks like someone's buttocks.