shill 
(shĭl) Slang
(shĭl) Slang n.
1. One who poses as a satisfied customer or an enthusiastic gambler to dupe bystanders into participating in a swindle.
2. One who publicly promotes another's cause, especially in an extravagant or misleading way.
v. shilled, shill·ing, shills
v.intr.
To act as a shill.
v.tr.
1. To act as a shill for (a deceitful enterprise).
2. To lure (a person) into a swindle.
[Perhaps short for shillaber, shill, of unknown origin.]