I used to be called a 'fluorescent lamp' -
slow in reacting.
"You are a fluorescent lamp, aren't you?"
"Fluorescent lamp? What do you... Oh, I see."
Something like that.
Do you have any euphemistic expression for
slow reaction? BTW, 'fluorescent lamp' is rather long and hard to pronounce. Is there a short form?
'Strip light' is a common expression for a 'fluorescent tube'.
Not so much a euphemism, more of an idiom - 'Not very quick off the mark' - slow to react at the start of a race. I can't think of anything else that means physically slow reactions - I've got plenty for being mentally 'slow'!
OK, here goes. These are normally not used as direct insults to a person - more when talking about them....unless you REALLY wish to insult their intelligence.
not the sharpest knife in the drawer / or tool in the box (not 'sharp' witted)
a sandwich short of a picnic (not quite enough intellegence)
not the full shilling (missing something)
not very bright (dim witted - play on words)
[not really an idiom, but] when brains were being handed out he was at the back of the queue (didn't get a full portion)
the lights are on but nobody's home (signs of life - but nothing intelligent happening in their head)
There are a lot more, but I can't remember them right now....I'm not in a particularily insulting mood today!