I used to play this one on Gaia!

Player 1 - POSTS A TABOO LETTER
Player 2 - POSTS A WORD WITHOUT THE TABOO LETTER, -and- A NEW LETTER
Player 3 - POSTS A WORD WITHOUT THE TABOO LETTER, -and- A NEW LETTER
And so on and so forth.

Let's start wiiiith:
TABOO LETTER = L

coffee

L