Airheaded and Off-the-wall

Airheaded adjective - Not having or showing an ability to absorb ideas readily.

Off-the-wall and airheaded are semantically related. In some cases you can use "Off-the-wall" instead an adjective "Airheaded".

Off-the-wall adjective - Different from the ordinary in a way that causes curiosity or suspicion.

Airheaded and off-the-wall are semantically related. Sometimes you can use "Airheaded" instead an adjective phrase "Off-the-wall".