Definition of broad
What is meant by wide is "a wide range of hands played". If a player is said to be playing wide, he is opening a wide range of hands. The player who plays wide finds reasons to play more hands than other players. You can tell this when you see the stats on your tracker or HUD. For example, at a full ring table, a typical player will play between 8% and 12% of his or her hands UTG. A player who plays large could play up to 35% of his UTG hands (sometimes more).
Large preflop, large postflop
Usually, players who play large preflop (one could also say, players who play too many hands) will also tend to play too many hands postflop. They will often overcall with pairs that have bad kickers, they will tend to overvalue their hands, they will tend to call big bets without the necessary odds. This is not the kind of player you want to bluff. These players will not be known for their hero-fold. Against this style of player, it is best to adopt a TAG style and bet big when you have a strong hand.