| twelfth cranial nerve | <anatomy, nerve> The hypoglossal nerve enervates the muscles of the tongue. Lesions of the twelfth cranial nerve result in deviation of the tongue toward the paralysed side and thick speech. Synonym: cranial nerve XII. (27 Sep 1997) |
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| twelfth-second | <physics> A unit for the measurement of small intervals of time, such that 10^12 (ten trillion) of these units make one second. Source: Websters Dictionary (01 Mar 1998) |
| twelfth-year molar | The second permanent molar tooth. (05 Mar 2000) |