'Tipster' definitions:

Definition of 'tipster'

From: WordNet
noun
One who sells advice about gambling or speculation (especially at the racetrack) [syn: tipster, tout]

Definition of 'Tipster'

From: GCIDE
  • Tipster \Tip"ster\, n. [Tip a hint + -ster.] One who makes a practice of giving or selling tips, or private hints or information, esp. for use in gambling upon the probable outcome of events, as horse races. [Webster 1913 Suppl.]