bicyclic

Having two cycles.

Having two rings of atoms in the molecule; the rings may be fused, as in naphthalene, or separate, as in biphenyl.

[…] substitution of a carboxylate would be expected to destabilize the dritterionic mesomer that contributes to the singlet valence bond description as the benzyne geometry becomes more bicyclic.

These geometries are almost reversed in the triplets. The 1,3-borazyne (III) shows more bicyclic character than the corresponding m-benzyne

A bicyclic compound.