diagonally upward
Refers to a direction or position that is upward and to the side, not straight above. Used in spatial descriptions.
The arrow points diagonally upward.
He looked diagonally upward.
completely unexpected direction; off-the-wall
Slang. Describes a development, outcome, or remark that goes in a direction nobody anticipated, often humorously or bizarrely. Frequently used in the phrase 予想の斜め上 (beyond expectations in an unexpected way).
His answers are always completely unexpected.
The movie's ending was totally off-the-wall.
Compound of 斜め (diagonal) and 上 (up). The slang sense likely derives from the idea of something coming from an angle that is not just above (expected) but off to the side, hence unpredictable.