The Tilt meter is a calculation that determines if your opponent may be getting tilty. The higher the Tilt meter gets, the more susceptible this player is to tilt. It’s calculated based on how active a player has been in the pot in recent hands, if they’ve lost one or more big pots recently, and if they are playing with more aggression than what is within their normal range. The Tilt meter takes into account ONLY recent activity, and will reduce its meter if a player begins playing more passively again, and doesn’t get involved in many pots. It’s another simple indicator you can quickly see that will alert you to looking into more stats and info on your opponent if you’re involved in a hand with them.
Disclaimer: Just because the tilt meter is full, doesn’t mean your opponent is definitely on tilt, but the likelihood of this is significantly increased based on normal patterns.