SCYLLA
Scylla
(noun) (Greek mythology) a sea nymph transformed into a sea monster who lived on one side of a narrow strait; drowned and devoured sailors who tried to escape Charybdis (a whirlpool) on the other side of the strait
Source: WordNet® 3.1
Scyl"la, n.
Definition: A dangerous rock on the Italian coast opposite the whirpool
Charybdis on the coast of Sicily, -- both personified in classical
literature as ravenous monsters. The passage between them was
formerly considered perilous; hence, the saying "Between Scylla and
Charybdis," signifying a great peril on either hand.
Source: Webster’s Unabridged Dictionary 1913 Edition