When it comes to speakers, "efficiency" is the % of electrical energy that the transducer converts into sound pressure -- the rest being converted into heat, etc...i.e., lost to our ears.
Sometimes this word is used by manufacturers to underline how loud their speakers/drivers can go when fed with a reasonable amount of W (i.e. energy). It sounds "marketing" to me...
Plus you have other manufacturers sporting interesting performance levels, to quote Trelja
who use drivers of 88 db/2.83 V sensitivity and then claim the speakers are 94 db/2.83 V sensitive
...
Would that be 94db @1M, both speakers fed a 1kHz sine wave, the mic on axis, 2ms gate / or is it that they have two drivers in parallel for each pass band / or?
