The Collaborative International Dictionary of English v.0.48:

Lentamente \Len`ta*men"te\ (l[asl]n`t[.a]*m[asl]n"t[asl]; E.
   l[e^]n`t[.a]*m[e^]n"t[-e]), adv. [It.] (Mus.)
   Slowly; in slow time.
   [1913 Webster]