Answer: dihedrals

AnswerCrossword Clue
dihedralsDIHEDRAL, the angle between two planes, also DIEDRAL
dihedralsAn angle formed by two plane faces
dihedralsA place where two planes of rock meet at an angle of between 60░ and 120░
dihedralsInclination of an aircraft's wing from the horizontal, esp. upward away from the fuselage