Usage examples for napping:

• It appeared to be spiteful because it had been caught napping "Tropic Days" – E. J. Banfield

• And the next time you are tempted to steal my chickens, just remember that I caught you napping and let you off when I might have shot you. "Old Granny Fox" – Thornton W. Burgess

• When not amusing herself by watching Brock's misfortunes, she was napping or reading or sending out for cool drinks. "The Husbands of Edith" – George Barr McCutcheon