Azaborane usually refers a borane cluster where BH vertices are replaced by N or NR (R stands typically for H or organic substituent). Like many of the related boranes, these clusters are polyhedra and can be classified as closo-, nido-, arachno-, etc.
Within the context of Wade's rules, NR is a 4-electron vertex, and N is a 3-electron vertex. Prominent examples are the charge-neutral nido- (i.e. ) and closo- (i.e. ).
Azaboranes can also refer to simpler compounds including iminoboranes (RB=NR', where R and R' stand typically for H or organic substituent) and borazines.