A fresbian is a friend of lesbians (at least one), who supports them and does not judge their lifestyle. Lesbians may bring intense drama to the lives of their heterosexual friends, but fresbians do not abandon them. On the contrary, they counsel and console the lesbians. Fresbians often reach a comfort level where they may joke about lesbianism, without it being offensive to their homosexual friend.
Mostly, fresbians do not actually engage in sexual acts together, and usually neither one of them is an actual lesbian- though this term is not meant to offend actual lesbians, who have most fresbians utmost respect.
"Oh god, I cannot believe Daniel just brokeup with me..."
"Do not worry, I will be your fresbian in your time of need. Let's go somewhere public and pretend that we are not interested in any of the men that look in our direction!"
"You're the best fresbian I've ever had!"