when your foot slips off your bicycle pedal, and the thing swings around and "checks" you in the shin.
can be very painful and messy if you were putting a lot of force down on it, especially if the pedal is pointy and metal for gripping shoes, as BMX pedals tend to be
tom: yo, i got a vicious pedal check riding my BMX last night.
jim: that sucks. i guess maybe you ought to wear shin guards with those beartrap pedals.