on the bubble

Prepositional phrase

1. Holding the last qualifying position with qualification still in progress, and thus liable to lose that position.
   • Smith was on the bubble but lost out when Jones was faster by a tenth of a second.
2. Having qualification for an event depend on the upcoming performances of other competitors; hence, at risk of being eliminated, and reversely, being close to qualification; on the verge.
   • The Knights had been on the bubble for the tournament, but played their way in by winning their last five games.
   • Most players play pretty loose on the bubble, much looser than they theoretically should, and even if I saw an opponent sitting out a few hands, it's more likely that he just hit a run of low cards than that he turned into a locksmith at this stage.2006, Dan Harrington, Bill Robertie, Harrington on Hold 'Em
3. (idiomatic) Uncertain of success.
   • The new bond issue now appears to be on the bubble, with support eroding.
4. Used other than figuratively or idiomatically: see on, bubble.
   • Among other aspects of bubble measurement, the researchers were interested in measuring the size of the bubble with a laser scattering technique. A laser is shone on the bubble, which scatters the light.2004, David D. Moon, Carbon Dating, Cold Fusion, and a Curve Ball, page 109