far out

Short definition from Wiktionary

Adjective

1. 1
   New, radical and extreme.
2. 2
   Used other than figuratively or idiomatically: see far, out.
3. 3
   Used other than figuratively or idiomatically: see far, out.
4. 4
   Very unusual, eccentric or unconventional

Interjection

1. 1
   Cool; great; an expression of support, enthusiasm, or celebration.
2. 2
   An expression of surprise.
3. 3
   An expression of displeasure.