1.NounThe trivalent radical R-C⋮ or any of its hydrocarbyl derivatives.
2.NounThe linear carbon allotrope, composed of alternating (1) triple and single bonds [ ...–C≡C–C≡C–... ] or (2) double bonds [ ...=C=C=C=... ].
3.NounLinear acetylenic carbon, a form of the linear carbon allotrope consisting of the form with alternating single- and triple-bonded carbons [ ...–C≡C–C≡C–... ].