A binary not. It inverts the bits in an integer.
(= Result bnot $78) /* the result will be $FF87 (0000000001111000b->1111111110000111b) */
(= Result bnot 0) /* the result will be $FFFF (0000000000000000->1111111111111111b) */
(= Result bnot $183D) /* the result will be $E7C2 (0001100000111101->1110011111000010b) */