I was engineering in undergrad and never really had any trouble, although my discipline (bioE) is generally much more gender-even than others.

However, in grad was the first time I worked side-by-side with people who were much older than me (anywhere from 5-25 years older than I). So being the only woman on a team, AND being the youngest, and part of me also thinks that since I was working with a lot of foreigners (I'm in the US), there might've been some cultural differences with regards to feminism/respect, I was pretty consistently spoken over or straight out ignored, even if it was 100% clear I was in the middle of talking. For example, one time we were watching a video of a medical procedure where I asked the guy with the laptop to pause for a second, as I had a point to make about a specific thing we were watching, and I'm literally mid-sentence when this 40-yr old male next to me just cuts me off and starts talking about something completely different. Then everyone starts entertaining his thoughts and eventually when he's done we go back to the video and I have to go "WAIT! I still want to talk about xyz" and have them repause it. Things like this happened over and over.

My ideas were also often discarded as worthless. For example, during brainstorming sessions, it's generally rule of thumb to not discount any idea, as stupid or ridiculous or technically/feasibly impossible as it is. Still, I come up with a pretty good idea, and am immediately shot down as "No that's dumb." A week later, this old professional business advisor comes in to talk with our team, and he brings up an idea that is literally the same idea I had, and everyone applauds him as it being a genius idea. Seriously. And then what I did next might be petty, but I was fed up with it and wanted to prove to them that I actually knew what I was talking about. I had a picture of our brainstorming board on my phone so I pull up the picture and zoom into the idea I had written and show one of the guys on our team "Yea! It is a cool idea, I had mentioned it last week too" and he waves me off going "Yea whatever" and then immediately goes back to asking the advisor more questions about it.

TL;DR - In undergrad, among peers, no sexism, and that's great because they're/we're the future :D. In grad, maybe it's a byproduct of people being older or working with more international people, but it's worse and sucks.