Adjective
nonbonding (not comparable)
(chemistry) Not involved in bonding
Bonding, antibonding, and nonbonding MOs When atomic orbitals interact, the resulting molecular orbital can be of three types: bonding, antibonding, or nonbonding. Source: Internet
However, if one or both these lone pairs is nonbonding then the M−N−R bond is bent and the extent of the bend speaks to how much pi bonding there may be. Source: Internet