off-the-wall

/AO1 F DH AH0 W AO0 L/
adjective
  1. 1

    Wildly unconventional; bizarre; absurd.

    โ€œShe is a very off-the-wall character.โ€

  2. 2

    Of a person's behaviour: greatly inappropriate.

Source: https://en.wiktionary.org/wiki/off-the-wall