onsight

From on +‎ sight.

onsight (not comparable)

1. (climbing) Without having previously seen the terrain.
   • 2007 July 18, Bill Becher, “Rock Climber Presumed Dead After Accident Off Irish Coast”, in New York Times‎^[1]:

     Reardon made hundreds of free-solo ascents of challenging climbing routes done onsight, meaning without rehearsal or practice.

onsight (third-person singular simple present onsights, present participle onsighting, simple past and past participle onsighted)

1. (climbing, transitive) To perform a climb without having previously seen the terrain.

• hosting, noights, thingos, toshing