1. A rim forming the edge of a sidewalk
2. An enclosing framework or border
3. A bit used with a bridoon for controlling a horse
1. To control; restrain; check
2. To cause to keep near the curb, as in 'curb your dog'
3. To furnish with or protect by a curb
4. To put on a curb
Curb, with the definition "strap passing under the jaw of a horse," dates to the late 15th century from Old French courbe ("curb on a horse"), which derives from Latin curvus from curvare ("to bend"). Ultimately the word derives from Proto-Indo-European *(s)ker- ("to turn, bend"). The meaning "enclosed framework" came about a century later in the 1510's, probably in keeping with the original notion of "curved." Curb as in "margin of stone between a sidewalk and road" is first attested in 1791 and is sometimes spelled kurb.
Now for the real reason I'm talking about curb today: