li·ber·o 
(lēbĕr-ō)
(lēbĕr-ō)n. pl. li·ber·os
In volleyball, a defensive player who can take the position of any backcourt player but cannot block or return the ball when it is higher than the net.
[Italian, free, from Old Italian, from Latin līber; see leudh- in the Appendix of Indo-European roots.]