Noun
line across a billiard table behind which the cue balls are placed at the start of a game
Source: WordNetbaulk line
Even if the cue ball is hit in exactly the same way, the nap will cause a different effect depending on whether the ball is hit down table (towards the black ball spot) or up table towards the baulk line. Source: Internet
If no "D" is drawn on the table then the "forward play" rule is followed: After a scratch, the player with ball-in-hand must shoot forward of the baulk line, i.e. towards the rack area, even if all legal balls are behind the baulk line. Source: Internet
The significance of this manoevre is that in advanced play, making a break that includes the tenth hoop (called 4-back) is penalized by granting the opponent a lift (entitling him to take the next shot from either baulk line). Source: Internet