RhymeZone: signum definitions

Definitions of signum:

noun: A sign, mark, or symbol.
noun: (historical) A medieval tower bell used particularly for ringing the 8 canonical hours.
noun: (mathematics) A function that extracts the sign of a real number x, yielding -1 if x is negative, +1 if x is positive, or 0 if x is zero.

(Definitions from Wiktionary)