phugoid

[fyoo-goid]
adjective Aerospace.
  1. of or relating to long-period oscillation in the longitudinal motion of an aircraft, rocket, or missile.

Origin of phugoid

1905–10; irregular < Greek phyg(ḗ) flight + -oid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018