WordNet (r) 3.0 (2006):

Bithynia
    n 1: an ancient country in northwestern Asia Minor in what is
         now Turkey; was absorbed into the Roman Empire by the end
         of the 1st century BC

Easton's 1897 Bible Dictionary:

Bithynia
   a province in Asia Minor, to the south of the Euxine and
   Propontis. Christian congregations were here formed at an early
   time (1 Pet. 1:1). Paul was prevented by the Spirit from
   entering this province (Acts 16:7). It is noted in church
   history as the province ruled over by Pliny as Roman proconsul,
   who was perplexed as to the course he should take with the
   numerous Christians brought before his tribunal on account of
   their profession of Christianity and their conduct, and wrote to
   Trajan, the emperor, for instructions (A.D. 107).


Hitchcock's Bible Names Dictionary (late 1800's):

Bithynia, violent precipitation