Four to the fourth
In text messaging, the number "4" consists of the letters: G, H, and I. With these letters, you are able to spell the word "high". Four to the fourth is an exponential term: 4 x 4 x 4 x 4. With T9 word, pressing the number "4" four times will spell out the word "high". Getting four to the fourth means to get high.
"Yo man, are we gettin four to the fourth this weekend?"