stāgnum

Lacuna denotes, in poetical language, any standing water, from a sea to a pool; lacus and stagnum are collections of standing water kept sound and fresh by their own springs, or by ebbing and flowing; lacus (liquere) is large enough to bring to mind the image of the open sea, in opp. to the main sea, like λίμνη; stagnum, like a pond, not so large as to resemble a lake, in opp. to a stream, like τέναγος; whereas palus and uligo are collections of standing water corrupted and grown foul; palus (πλυδᾶν) is, like a marsh, a district covered with a surface of foul water, like ἕλος; uligo (from ὀλός) like a moor, a district soaked through with foul water. The palus appears as a mass of water made thick by mud and bog-earth, in which a person may be drowned; uligo only as ground thoroughly soaked with water, in which a man may sink down. Lastly, lamæ and lustra denote standing waters of small extent; lama, a mere dirty and filthy puddle on a high road; lustra, an ill-smelling and noisome quagmire in woods, etc. (v. 30.)