What's with the stink eye?

I have noticed on occasion that I get the "stink eye" from some other women. One example is some neighbors I had. The guy that was living there was very friendly and we would always acknowledge each other during passing (neighborly acknowledge, nothing flirtatious) His wife (or girlfriend, not sure which) wouldn't give me the time of day, let alone acknowledge me. It seemed I was always getting the "stink eye" from her. I've had this happen from others on other occasions. And mainly from women who are with a man. What's up with this? I only get it from other women.
What's with the stink eye?
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