Lewis Short
(adverb) : guttātim, gutta
* By drops, drop by drop (ante- and post-class.): lacrimae guttatim cadunt, Enn. ap. Non. 116, 1 (Trag. v. 238 Vahl.): pluvia guttatim labitur,Arn. 2, 84; App. M. 3, p. 130: cor guttatim contabescit,Plaut. Merc. 1, 2, 92.
Charlton T. Lewis, Charles Short, A Latin Dictionary