| systems jock | T | |
| tail recursion | talk mode | |
| talker system | TAN | |
| tanked | TANSTAAFL | |
| tape monkey | tar and feather | |
| tarball | tardegy | |
| taste | tayste | |
| TCB | TCP/IP | |
| TECO | tee | |
| teergrube | teledildonics | |
| ten-finger interface | tense | |
| tentacle | tenured graduate student | |
| tera- | teraflop club | |
| terminak | terminal brain death | |
| terminal illness | terminal junkie | |
| test | TeX | |
| text | thanks in advance | |
| That's not a bug, that's a feature! | the literature | |
| the network | the X that can be Y is not the true X | |
| theology | theory | |
| thinko | This can't happen | |
| This time, for sure! | thrash | |
| thread | three-finger salute | |
| throwaway account | thud | |
| thumb | thundering herd problem | |
| thunk | tick | |
| tick-list features | tickle a bug | |
| tiger team | time bomb | |
| time sink | time T | |
| times-or-divided-by | timesharing | |
| TINC | Tinkerbell program | |
| TINLC | tip of the ice-cube | |
| tired iron | tits on a keyboard | |
| TLA | TMRC | |
| TMRCie | TMTOWTDI | |
| to a first approximation | to a zeroth approximation | |
| toad | toast | |
| toaster | toeprint | |
| TOFU | toggle | |
| tool | toolchain | |
| toolsmith | toor | |
| top-post | topic drift | |
| topic group | TOPS-10 | |
| TOPS-20 | TOS | |
| tourist | tourist information | |
| touristic | toy | |
| toy language | toy problem | |
| toy program | trampoline | |
| trap | trap door | |
| trash | trawl | |
| tree-killer | treeware | |
| trit | trivial | |
| troff | troglodyte | |
| troglodyte mode | Trojan horse | |
| troll | Troll-O-Meter | |
| tron | troughie | |
| true-hacker | tty | |
| tube | tube time | |
| tunafish | tune | |
| turbo nerd | Turing tar-pit | |
| turist | Tux | |
| tweak | TWENEX | |
| twiddle | twilight zone | |
| twink | twirling baton | |
| two pi | two-to-the-N | |