T3

Noun

 * 1)  A tax reporting form used by estates and trusts.
 * 2)  A transit lane restricted to vehicles with a minimum of three occupants.
 * 1)  A transit lane restricted to vehicles with a minimum of three occupants.

Proper noun

 * 1)  A proprietary network protocol.
 * 2)  A network backbone connection equivalent to 28 T1 lines, typically fiber optic.