interjection
(slang) Draws attention to an act of foolishness or stupidity.
(slang) A placeholder for unimportant details, blah blah blah.
verb
(slang) To act stupidly or foolishly.
(slang) To make a stupid mistake.
(slang) To have one's eyes pointing in different directions; to exhibit strabismus.
noun
(slang) A person who acts stupidly or foolishly; a person who derps.
(slang) A stupid mistake, stupidity.
(uncountable) The constant repeating of an opinion after facts have proved it incorrect, especially as a rhetorical tactic.