A change in attitude of an aircraft on an axis other than the one you at first expected.
Correcting for this behaviour is the proper use of co-ordinated control.
For example, applying aileron will primarily roll an aircraft, but the extra induced drag
on the wing which has more lift will pull that wing backwards, resulting in adverse yaw which must
be countered by the application of rudder.
Likewise, applying rudder causes one wing to fly faster than the other (around the outside of your turn),
resulting in increased lift and a roll into the turn.