perverse sheaf
bounded cochain complex C of constructible sheaves over a topological space, such that, for all integers i, the support of ℋ⁻ⁱ(C) has dimension at most 2i, and similarly for the dual complex of C, where ℋ denotes the cohomology sheaf
en-GB/pəˈvɜːs ˈʃiːf/
en-US/pɚˈvɝs ˈʃif/