Final answer:
The expression 'turn a blind eye to something' means to ignore or pretend not to see something.
Step-by-step explanation:
The expression 'turn a blind eye to something' means to ignore or pretend not to see something. It refers to deliberately choosing not to notice or acknowledge something, usually because it may be uncomfortable or inconvenient to deal with. For example, if someone witnesses a friend cheating on a test but decides not to say anything, they are 'turning a blind eye' to the cheating.