/ ʃəʊl; NAmE ʃoʊl/ noun
1.
a large number of fish swimming together as a group
—compare school (9)
2.
a small hill of sand just below the surface of the sea
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WORD ORIGIN
sense 1 late 16th cent.: probably from Middle Dutch schōle troop. Compare with school sense 9.
sense 2 Old English sceald (adjective), of Germanic origin; related to shallow .