RUSTLED (UP) can be defined as to have been SCARED or startled, usually by a sudden noise. The crossword solution SCARED (6 letters) is an appropriate word to describe this term, as it means to be filled with fear or terror. This term is often used in the context of animals being startled by a loud noise, such as a gunshot or a loud bang. It can also be used to describe people who are startled by a sudden sound or movement.