cowabunga

As an interjection cowabunga

is (slang) an expression of surprise or amazement, often followed by "dude".

As an adjective outrageous is

cruel, violating morality or decency; provoking indignation or affront.

As interjections the difference between kowabunga and cowabunga

is that kowabunga is while cowabunga is (slang) an expression of surprise or amazement, often followed by "dude".