It's when a guy from another department walks into a room and asks for a developer, unconsciously ignores the female developer closest to him and starts addressing the male developer.
It's when a guy kindly asks a woman to stop debating a technical spec because she wouldn't understand the details (even though she's more technical than he is).
It's when a sales guy makes a joke with his female colleague that her eye makeup is what is closing deals that day.
I don't know about other departments coming in to ask for an engineer, but when it's an engineer looking for another engineer on a different team, it usually takes the form of asking openly in that teams hipchat/slack/irc room (as gender neutral as it gets) or specifically addressing one particular engineer (usually because that engineer is known for being great at providing advice or technical details on the issue at hand)
I've never once witnessed that second one and would be shocked if I did witness that. I've been around long enough that if that were still a problem, I would expect to have witnessed it firsthand.
I know the third happens (my sister is in sales and has been subjected to it).
Things like "... can you guys give me a hand." apparently.
I think it's a combination of things... on the one hand there is outright descrimination and bias... on the other, society is leaning towards overtly sensitive to anything that could be considered insensitive or biased.
It's when a guy kindly asks a woman to stop debating a technical spec because she wouldn't understand the details (even though she's more technical than he is).
It's when a sales guy makes a joke with his female colleague that her eye makeup is what is closing deals that day.