
• (n.) The reading of the leveling staff in its unchanged position when the leveling instrument has been taken to a new position; a sight directed backwards to a station previously occupied. Cf. Foresight, n., 3.
Found on
http://thinkexist.com/dictionary/meaning/backsight/

Back'sight` (-sīt`) noun [ Back , adverb + sight .] (Surv.) The reading of the leveling staff in its unchanged position when the leveling instrument has been taken to a new position; a sight directed backwards to a station previously occupied. Confer Foresight ,
Found on
http://www.encyclo.co.uk/webster/B/3
No exact match found.