A snoop is someone who snoops around, which means they secretly look or listen for information that's not meant for them.
When people say "I don't want to be a snoop," it usually means they're talking about being nosy and prying into others' business. They might also use the word in relation to something suspicious going on – like if someone is snooping around the house at night, you could guess that something's up.
The act of snooping
To be devious and cunning so as not to be seen.
