A player on the offense who is able to receive a forward pass. Eligible receivers include the players on the end of the offensive line and the players who are at least a yard behind the line of scrimmage. Non-eligible receivers include most of the offensive line with the center, guards, tackles, etc. not able to receive a forward pass, as well as the quarterback under the T-formation.
Ineligible receivers are unable to catch a forward pass either in front or behind the line of scrimmage, as well as being unable to move upfield before the pass is thrown and passes the line of scrimmage.