blindfish

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of various small fishes, such as the cavefish, that have rudimentary, nonfunctioning eyes and inhabit the waters of caves and underground streams.

Century Dictionary and Cyclopedia

1. n. A cave-fish, one of the Amblyopsidæ, having eyes rudimentary and useless for vision. The best-known is the Amblyopsis spelæus, or blind-fish of the Mammoth Cave of Kentucky; another is Typhlichthys subterraneus. Amblyopsis spelæus attains occasionally a length of 3 to 5 inches; it has rudimentary and functionless eyes, and ventral fins small and of 4 rays each. The color is pale as if bleached. It inhabits the subterranean streams of Kentucky and Indiana, especially those in the Mammoth Cave. Typhlichthys subterraneus is a much smaller species and destitute of ventral fins. It is an occasional associate of the Amblyopsis. See cut under Amblyopsis.
2. n. A myzont of the family Myxinidæ, Myxine glutinosa; the hag.
3. n. Any of the several species of fishes which inhabit caves and have more or less rudimentary eyes.

Wiktionary

1. n. Any of various fish, having only rudimentary eyes, that inhabit underground waters

GNU Webster's 1913

1. n. A small fish (Amblyopsis spelæus) destitute of eyes, found in the waters of the Mammoth Cave, in Kentucky. Related fishes from other caves take the same name.