Definition of longilateral in US English:

longilateral

adjective

Mathematics
  • Of a number: expressible as the product of two whole numbers that differ by 1 (as 12, = 3 × 4, and 56,= 7 × 8); (of a plane figure) represented by such a pair of numbers; not quite square, (also) long and narrow.

Origin

Mid 17th century; earliest use found in Thomas Browne (1605–1682), physician and author. From post-classical Latin longilaterus long-sided + -al.