[mid-19C+] a fool; thus look an absolute tit, look a right tit, to appear a total fool, thus the school ‘witticism’, I feel a right tit.
[1960s–70s] (US) an important person, or one who thinks they are.
[2000s] to make a fool of oneself.
[20C+] said of one who is lost in thought, abstracted.
[1940s+] to play around, to waste time, to act in a trivial, pointless manner.