Is hydroboration a pericyclic reaction?
Based on the IUPAC Goldbook definition, the only two requirements for a pericyclic reaction are:


Concerted mechanism
Cyclic transition state


Hydroboration reactions (and similar reactions) are pericylic reactions by these criteria, as are all cheletropic reactions.

The language about fully conjugated transition states can be used to explain some pericyclic reactions, but not all, and thus IUPAC uses the phrasing may be viewed as.... Hydride shifts, (and all sigmatropic rearrangements ene reactions) involve non-$\pi$ orbitals (even so, the transition states do tend to follow the Hückel rule).