1. Someone who drives very fast in their car, especially over the legal speed limit. I used to be an awful speed merchant, but I got so many tickets that I nearly lost my license. OK, I know we're running late, but there's no need to be such a speed merchant. I'd rather arrive alive.

2. An athlete who runs, skates, swims, cycles, etc., very fast. The team's new running back is one hell of a speed merchant. The speed merchant already had eight Olympic gold medals for cycling, and he finally added a Tour de France championship to his list of accolades.

3. Someone or something that performs an action much faster than is usual. I can't believe you've already read through all these reports. You're a real speed merchant! Th tablet's new CPU is a speed merchant, all right, but it eats through the battery like nobody's business.