The Collaborative International Dictionary of English v.0.48:

Lentitude \Len"ti*tude\ (l[e^]n"t[i^]*t[=u]d), n. [L. lentitudo,
   fr. lentus slow: cf. OF. lentitude. See Lent, a.]
   Slowness; sluggishness. [Obs.]
   [1913 Webster]