I would like to thank you all very much for your suggestions and let you know "k" has but one parent and he has difficulty discussing things of that nature with her. I'm sure he will find a way. Thanks again.

Personally, I would want such a conversation between me and my child. So I would suggest that you tell the parents about the conversation and let them decide how best to discuss the subject.

 I presonally feel this delicate subject should be left to her parents to decide how to handle the subject.

For me I feel she is still to young to take in the meaning of such a word.

My first question would be why an 8 year old was watching that sort of movie... but anyway it depends how your grand daughter's parents want to handle the situation. If you were to explain it to her without her parents permission you could get in to quite a heated debate. So firstly I would approach them and if they wanted you to let her know, then explain it to her. Or alternatively you could take her to go see a nurse who could explain it to her. Alternatively you could just ignore it until she hits age 12ish where it will be explained with parental permission by a sexual ed teacher.