Plain English Meaning
When two forces pull on something in different directions, they add up to one overall force that points somewhere between them. That combined force is the resultant.
Full Definition
In aerodynamics, the single combined force produced when two or more separate forces act on an object at the same time. In a level turn, the resultant is the combined effect of the vertical component of lift (which holds the airplane up) and the horizontal component of lift (which pulls the airplane around the turn).
Context Anchor
Seen in discussions of level turns, bank angle, and the load the airplane must support while turning.
Derivation
From the Latin resultare, meaning 'to spring back' or 'to follow as a consequence.' The resultant is the force that 'results' when other forces are combined.
Why Pilots Care
The magnitude of the resultant determines how much total lift the must produce, directly affecting and load in .