blindfish

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

• noun A cavefish.

from The Century Dictionary.

• noun Any of the several species of fishes which inhabit caves and have more or less rudimentary eyes.
• noun A cave-fish, one of the Amblyopsidæ, having eyes rudimentary and useless for vision.
• noun A myzont of the family Myxinidæ, Myxine glutinosa; the hag.

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

• noun 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.

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

• noun Any of various fish, having only rudimentary eyes, that inhabit underground waters