| Noun | 1. | Ac - a radioactive element of the actinide series; found in uranium oreschemical element, element - any of the more than 100 known substances (of which 92 occur naturally) that cannot be separated into simpler substances and that singly or in combination constitute all matter uranium ore - any ore from which uranium can be extracted |
| 2. | AC - an electric current that reverses direction sinusoidally; "In the US most household current is AC at 60 cycles per second"electrical energy, electricity - energy made available by the flow of electric charge through a conductor; "they built a car that runs on electricity" |