High and low are pretty universal because it is basically the same terminology as for cars, but I've had bike shop guys make me specify what I mean because enough people get them confused that they can't take it for granted.
"Bicycle talk" encompasses talk with people of all levels of knowledge, so if I am talking with someone knowledgeable, I will use ratios. If I'm talking to a beginner, I will say high or low, and make sure they understand high means big in the front and small in the back, and the other way around for low. It helps them both know what to call them and helps them understand how they work.

​ I know that is more than you asked for, but as you gain knowledge about bikes, I think it's also useful to know how people pass it on. If you ever ride ride with a kid or a beginner, I hope you find this useful. It's also important to remember that a kid has never driven, so high and low is really meaningless to them, and it's not intuitive that harder to pedal can mean faster.