Denshi Jisho — Online Japanese dictionary

返す かえす 1: to return (something); to restore; to put back;
2: to turn over; to turn upside down; to overturn;
3: to pay back; to retaliate; to reciprocate;
4: () (after the -masu stem of a verb) to repeat ...; to do ... back
Common word, Godan verb with su ending, Transitive verb 
返す返す かえすがえす repeatedly; to a tremendous extent
Adverb 

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