(graph theory) A mathematician or computer scientist who specializes in graph theory

An algebraist who specializes in ring theory

Beelzebub; Satan / (idiomatic, biblical) a ruler over a worthless kingdom; leader of a meaningless microcosm.

(American football) To move the chains. / (idiomatic) To make progress, as used in political and corporate venues to express proactive actions.

(idiomatic) To accept or confront the unpleasant consequences of one's actions.

(idiomatic, pharmacology, medicine) Of drugs, dispensed by a pharmacist without needing a doctor's prescription or other form of compliance.

(idiomatic) A traveler.

(mathematics) A mathematician who specializes in number theory

Offered for sale. / During a real estate auction: going to be sold at that auction, i.e. the bid has reached the vendor's reserve.

(idiomatic) A small and seemingly insignificant addition to a burden that renders it too much to bear; the small thing which causes failure, or causes inability or unwillingness to endure any more of something.