1. T3 - Noun
2. T3 - Proper noun
(biochemistry) Abbreviation of triiodothyronine.
(Canada) A tax reporting form used by estates and trusts.
(Australia) A transit lane restricted to vehicles with a minimum of three occupants.
(networking) A proprietary network protocol.
(networking) A network backbone connection equivalent to 28 T1 lines, typically fiber optic.
Source: en.wiktionary.org