Having two parts.
Having two participants; joint.
Having vertices that can be divided into two independent sets (see bigraph)
Divided into two at the base.
Having two separate parts, often adjoined by a line (or sometimes a space), e.g. Wright-Phillips.
Used other than figuratively or idiomatically: see double, barrelled. Having two barrels, as a gun.
Twofold, having a double purpose or nature.
Forceful, powerful (like a double-barrelled shotgun).