Definition
A triangle that does not contain a right angle (90°). All three of its interior angles are either acute (less than 90°) or one is obtuse (greater than 90°), but none is exactly 90°.
Plain English
Any triangle that doesn't have a square corner in it.
Context Anchor
Seen in flight planning and navigation calculations, especially when working with wind triangles.
Derivation
From the Latin obliquus, meaning 'slanting' or 'sideways.' An oblique triangle is one whose sides and angles are 'slanted' — none sit squarely at 90° to another.
Why Pilots Care
Enables accurate solutions for headings and speeds when standard right-triangle shortcuts cannot be used.
Intuition Check
Oblique does not mean unclear or indirect here. It means the triangle has no 90-degree angle.
Example Sentence 1
Because the wind triangle formed an oblique triangle, the student used the law of cosines to solve for groundspeed.
Example Sentence 2
After plotting the true course and wind vector, the resulting oblique triangle gave us the drift angle.