| TAC | measuring instrument for indicating speed of rotation |
|---|---|
| TAC | abnormally rapid heartbeat (over 100 beats per minute) |
| TAC | echidnas |
| TAC | type genus of the family Tachyglossidae |
| TAC | a basic or basalt glass |
| TAC | a theodolite designed for rapid measurements |
| TAC | a genus of Limulidae |
| TAC | indicated by necessary connotation though not expressed directly |
| TAC | (law) tacit approval of someone's wrongdoing |
| TAC | in a tacit manner |
| TAC | habitually reserved and uncommunicative |
| TAC | the trait of being uncommunicative |