look up any word, like pussy:
 
1.
mentally challenged or crazy.

an old London expression for someone either a bit simple or downright psychotic.

often found lurking in re-runs of "The Sweeney" or "Minder"
"Why is that bloke walking round in circles?"

"Dunno, I reckon he's a bit diddle-o"
by Dougal474 October 26, 2006