One who takes to (or continues) learning
late in life. An old dog
who thinks he can learn new tricks
The English usage dates from after the introduction of
opsimathy, "learning acquired late in life,"
from the Greek opsimathein, 'late learning',
in the 17th Century.
The sense is often derogatory, implying the learning should have
been done earlier. A modern example from the web:
This progress has sometimes exposed him as an
opsimath, discovering important theological texts only
late in his career.
There are signs, though, of an emerging positive sense, as
shown by the existence of several 'Opsimath clubs' around the
place, where older folks enjoy learning stuff.
Great idea though it is, at a mere 118 Google hits you'd
have to say this word is pretty marginal.
info from http://www.funwords.com/library/o.htm, quote from http://www.firstthings.com/ftissues/ft9603/articles/revessay.html