Definition of halfback noun from the Oxford Advanced Learner's Dictionary
halfback
noun
ˈhɑːfbæk ˈhæfbæk
(alsohalf)
1[countable]one of the defending players in hockey or rugby whose position is between those who play at the front of a team and those who play at the back2 (alsotailback)[countable]one of the two attacking players in American football whose position is behind the quarterback and beside the fullbacks3 (alsotailback)[uncountable]the position a halfback plays at