The point and time when a situation becomes "Too Much". The breaking point where you feel like you must get out now, or you might start to panic. Similar to claustraphobia, however it usually involves a Cluster-Fuck situation.
Girl we are about to have to go right now. I'm about to get clusterphobic.
1. An acute fear that certain types of social or performance situations will definately go bad leading to avoidance behavior.
2. Irrational anxiety elicited by even the thought of exposure to an insuing cluster-fuck.
My sister is so clusterphobic, every time she is asked to help plan an event or holiday party she will throw a shoe just trying to run away.