Plain English Meaning
The nose-up position the airplane is held in just as it touches down, so the main wheels land before the nose wheel.
Full Definition
The pitch attitude of the airplane at the moment of touchdown, with the nose raised so the main wheels contact the runway first while the wings are at a high angle of attack near the stall.
Context Anchor
You encounter this term during the round out and flare, when the pilot changes from descending toward the runway to settling onto it for touchdown.
Derivation
Attitude originally referred to the posture or of a . In , it means the posture of the airplane in the : how the nose and wings are positioned. Landing attitude is that airplane posture at the moment of .