Horizontal curly brace underneath, an underbrace used in math to annotate or group part of an equation from below.
256 characters in the Miscellaneous Technical Unicode block, from number 224.
U+23DFBOTTOM CURLY BRACKETU+23E0TOP TORTOISE SHELL BRACKETU+23E1BOTTOM TORTOISE SHELL BRACKETU+23E2WHITE TRAPEZIUMU+23E3BENZENE RING WITH CIRCLEU+23E4STRAIGHTNESSU+23E5FLATNESSU+23E6AC CURRENTU+23E7ELECTRICAL INTERSECTIONU+23E8DECIMAL EXPONENT SYMBOLU+23E9BLACK RIGHT-POINTING DOUBLE TRIANGLEU+23EABLACK LEFT-POINTING DOUBLE TRIANGLEU+23EBBLACK UP-POINTING DOUBLE TRIANGLEU+23ECBLACK DOWN-POINTING DOUBLE TRIANGLEU+23EDBLACK RIGHT-POINTING DOUBLE TRIANGLE WITH VERTICAL BARU+23EEBLACK LEFT-POINTING DOUBLE TRIANGLE WITH VERTICAL BARU+23EFBLACK RIGHT-POINTING TRIANGLE WITH DOUBLE VERTICAL BARU+23F0ALARM CLOCKU+23F1STOPWATCHU+23F2TIMER CLOCKU+23F3HOURGLASS WITH FLOWING SANDU+23F4BLACK MEDIUM LEFT-POINTING TRIANGLEU+23F5BLACK MEDIUM RIGHT-POINTING TRIANGLEU+23F6BLACK MEDIUM UP-POINTING TRIANGLEU+23F7BLACK MEDIUM DOWN-POINTING TRIANGLEU+23F8DOUBLE VERTICAL BARU+23F9BLACK SQUARE FOR STOPU+23FABLACK CIRCLE FOR RECORDU+23FBPOWER SYMBOLU+23FCPOWER ON-OFF SYMBOLU+23FDPOWER ON SYMBOLU+23FEPOWER SLEEP SYMBOLU+23FFOBSERVER EYE SYMBOL