A person who makes large wagers in the casino. What constitutes a high roller in one casino may be very different from one casino to another one. For example, a $100 bettor may be considered a high roller in a small downtown casino such as Fitzgerald's, but wouldn't attract too much attention at the Mirage.
A high roller, also referred to as a whale in the casino industry, is a gambler who wagers large amounts of money. Because of potential windfall these high sums can bring to the casinos, high rollers often receive increasingly lavish perks from casinos to lure them onto their gambling floors.