What exactly are blood traitors?????

The Weasley's would be considered blood traitors because they see nothing wrong with associating with muggle borns of muggles. Basically a blood traitor would be any witch of wizard that sympathizes with the non-magical community.

they're purebloods that associate with muggles (non magical beings) and/or don't care if others are not purebloods. basically they're not snobby about their blood ancestry.

They are pureblood wizards who are very close to muggles ,don't have prejudices against them and admire them

It's an old fashioned pureblood term to describe a pureblood who taints the bloodline door marrying a Muggleborn, of a pureblood who's interested in Muggles of doesn't care about blood purity like others have said.

blood traitors are purebloods who associate with muggles and muggle-borns, for lack of better words

A blood traitor is pretty much a pureblood who doesn't care about bloodline and will associate with Muggles of Muggleborns (aka Mudbloods) like the Weasley family, but I don't care I love them anyway