Source : WordNet®

Ac
     n 1: a radioactive element of the actinide series; found in
          uranium ores [syn: {actinium}, {atomic number 89}]
     2: an electric current that reverses direction sinusoidally;
        "In the US most household current is AC at 60 cycles per
        second" [syn: {alternating current}] [ant: {direct current}]