The Collaborative International Dictionary of English v.0.48:

Est \Est\, n. & adv.
   East. [Obs.] --Chaucer.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

-est \-est\ (-[e^]st). [AS. -ost, -est; akin to G. -est, -ist,
   Icel. -astr, -str, Goth. -ists, -[=o]sts, Skr. -ish[.t]ha.]
   A suffix used to form the superlative of adjectives and
   adverbs; as, smoothest; earl(y)iest.
   [1913 Webster]

WordNet (r) 3.0 (2006):

EST
    n 1: standard time in the 5th time zone west of Greenwich,
         reckoned at the 75th meridian; used in the eastern United
         States [syn: Eastern Time, Eastern Standard Time,
         EST]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

EST
       Eastern Standard Time [-0500] (TZ, EDT, USA)