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sleep·er (slēpər)
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n.
1. One that sleeps: a heavy sleeper who was not wakened by the burglar.
2. A sleeping car.
3. often sleepers Children's pajamas, usually with legs that cover the feet.
4.
a. One that achieves unexpected recognition or success, as a racehorse or movie.
b. A spy or saboteur who is planted in an enemy country and who lives unobtrusively as a citizen of that country until activated into clandestine operations by a prearranged signal.
5. A horizontal structural member on or near the ground that supports weight.
6. Chiefly British A railroad crosstie.
7. Any of various chiefly tropical fishes of the family Eleotridae of fresh, brackish, and shallow marine waters, resembling the gobies but without fused pelvic fins and noted for their habit of lying immobile.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.

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