Young homeless people and panhandlers who congregate around Mill Avenue in downtown Tempe, Arizona. Though often used as a derogative term, it is also used by the street people to describe themselves.

Probably coined as a variant of mallrat, with "mall" replaced by Mill Avenue.
Those panhandlers aren't ASU students, dude, they're Millrats.
by M S November 18, 2004
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The act of servicing production workers through the washrooms glory hole with the promise that said production worker will break something so the millrat can get overtime.
Dang, old boy just bought a new motorcycle, he really must have did the Gary Millrat to be able to afford that!
by TheAlmightyRod August 29, 2023
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