The term 'Knot Up' can be defined by four crossword solutions: TIE (3 letters), ENSNARL (7 letters), ENTANGLE (8 letters), and SNARL (5 letters). TIE is the act of fastening two objects together with a rope or string. ENSNARL is to ENTANGLE something in a complicated way. ENTANGLE is to twist together or intertwine, often in a complex or confused manner. SNARL is to become or make tangled or intertwined. All of these words describe the act of knotting up something, which is the act of tying something in a complex or tangled manner.