What is Holder In Due Course?

Legal Definition
The holder in due course (HDC) theory is a rule in commercial law that protects a purchaser of debt, where the purchaser is assigned the right to receive the debt payments. The theory insulates the purchaser of debt, or other obligation to pay, against charges that either party to the original transaction might have had against the other.
-- Wikipedia
Legal Definition
A term for the original holder of an instrument that takes it in good faith and exchanges something valuable for it. AKA protected holder.
Legal Definition
in English law, is "a holder who has taken a bill of exchange (check or note) complete and regular on the face of it, under the following conditions, namely; (a) That he became the holder of it before it was overdue, and without notice that it had been previously dishonored, if such was the fact, (b) That he took the bill (check or note) in good faith and for value, and that at the time it was negotiated to him he had no notice of any defect in the title of the person who negotiated it." Bills of Exchange Act, 1882, (45 & 46 Viet c. 61, § 29.) And see Sutherland v. Mead, 80 App. Div. lO3, 80 N. Y. Supp. 504.
-- Black's Law Dictionary