1. 
[syn: seriously, earnestly, in earnest]
The Collaborative International Dictionary of English v.0.48:
Earnest \Ear"nest\ ([~e]r"n[e^]st), n. [AS. eornost, eornest;
   akin to OHG. ernust, G. ernst; cf. Icel. orrosta battle,
   perh. akin to Gr. 'orny`nai to excite, L. oriri to rise.]
   Seriousness; reality; fixed determination; eagerness;
   intentness.
   [1913 Webster]
         Take heed that this jest do not one day turn to
         earnest.                                 --Sir P.
                                                  Sidney.
   [1913 Webster]
         And given in earnest what I begged in jest. --Shak.
   [1913 Webster]
   In earnest, serious; seriously; not in jest; earnestly.
      [1913 Webster]
WordNet (r) 3.0 (2006):
in earnest
    adv 1: in a serious manner; "talking earnestly with his son";
           "she started studying snakes in earnest"; "a play dealing
           seriously with the question of divorce" [syn:
           seriously, earnestly, in earnest]