Source : Webster's Revised Unabridged Dictionary (1913)

Proverbially \Pro*ver"bi*al*ly\, adv.
   In a proverbial manner; by way of proverb; hence, commonly;
   universally; as, it is proverbially said; the bee is
   proverbially busy.

Source : WordNet®

proverbially
     adv : in the manner of something that has become a byword; "this
           proverbially bitter plant, wormwood"