What does dingus mean?

"Dingus" means roughly the same as "doodad", "thingummy", "thingy" or "whatchamacallit" - normally a placeholder for the name of something whose proper name does not immediately spring to mind.

For example, if you were explaining how to multiply:

##(x+1)(2y+xy-3x^2+4)##

you might call the polynomial in the second pair of parentheses a "dingus", not remembering the proper name for an expression with four terms (is it "quaternary"?).