An endearing term for a graduate student, usually going for a Piled High and Deeper, who has been conned into "helping" their advisor by lecturing "a few" sessions of a class, without really knowing what they're talking about, and so end up either going by their advisor's shitty lecture notes or rambling about their thesis for three hours a week.

Thankfully, at my university's CS department there's only one or two professors who engage in such lectroid abuse, but given the size of the department that amounts to a good 8-10%. At least they keep it to a minimum, though when I took CS272 I actually thought the lectroid was the professor. (Incidentally, this professor is also probably the worst culprit of research assistant abuse in other areas as well.)