Um, yes I do. It's where you blow a substantial lead in a match while looking firmly in control, you could choke the match away or lose the lead you've earnt but still win the match later.
No, it really isn't. Players lose matches. Players make comebacks. The player who gets off to the better start often can't sustain it - that's not choking, that's just tennis - especially when it's a lower ranked player!
I didn't see today's match, but against Stakhovsky Evans definitely did not 'choke'. It was a very, very close match for two sets with Evans creating chances but the higher ranked player stepping it up every time. The lower ranked player than eventually was unable to sustain his level and the vast experience and quality higher ranked player eventually shone through.
Choking had absolutely nothing to do with it.
Now I didn't see the match today but going by those that did, Evans was doing well but again his level dropped and his opponent outplayed him. But losing in three sets, with only the one break difference in each, having not had a 'significant' lead in any of them, is NOT choking.
It really is tiresome when some people label any defeat as a 'choke'. When Murray lost to Cilic the other day, did he choke? Of course he didn't - the better player won on the day. Such is tennis.