Improper movement

Improper movement is a illicit movement from an A-bar-position to an A-position, as in (i):

(i) * [IP Johni seems [CP t'i [IP ti knows it all]]]

The intermediate trace, t'i, being a variable since it occupies an A-bar position, violates principle C of the Binding Theory, because it is A-bound by John.

Link
Utrecht Lexicon of Linguistics