clingfish

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various small marine fishes of the family Gobiesocidae, having a large sucking disk under the front part of the body by which they fasten themselves to rocks and seaweed.

from The Century Dictionary.

• noun Any species of fish belonging to the suborder Xenopterygii, small fishes living chiefly in shallow pools among the rocks, and having a ventral sucking-disk with which they are enabled to cling to any object.

from the GNU version of the Collaborative International Dictionary of English.

• noun very small (to 3 inches) flattened marine fish with a sucking disc on the abdomen for clinging to rocks etc.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A small marine fish of the family Gobiesocidae which has a sucking disc on its underside that it uses to cling to rocks and seaweed.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun very small (to 3 inches) flattened marine fish with a sucking disc on the abdomen for clinging to rocks etc.