WordNet sense 1 (1/60 of a minute; the basic unit of time adopted under the Systeme International d'Unites):

sec, second

WordNet sense 2 (an abundant tasteless odorless multivalent nonmetallic element; best known in yellow crystals; occurs in many sulphide and sulphate minerals and even in native form (especially in volcanic regions)):

sulfur, sulphur

WordNet sense 3 (the cardinal compass point that is at 180 degrees):

south, southward, due south

WordNet sense 4 (a unit of conductance equal to the reciprocal of an ohm):

mho, Siemens, reciprocal ohm

WordNet sense 5 ((thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work):

entropy, randomness