Football. (of a forward pass) not completed; not caught by a receiver.
Engineering. noting a truss the panel points of which are not entirely connected so as to form a system of triangles. Compare complete (def 8), redundant (def 5c).
Logic, Philosophy. (of an expression or symbol) meaningful only in a specific context. (of a set of axioms) such that there is at least one true proposition (able to be formulated in terms of the basic ideas of a given system) that is not deducible from the set. Compare complete (def 7).
Education. a temporary grade indicating that a student has not fulfilled one or more of the essential requirements for a course: If I don't hand in my term paper for last semester's English course, the professor is going to change my incomplete to an F.