Definition of "surreptitiously"

They stayed together during three dances, went out on to the terrace, explored wherever they were permitted to explore, paid two visits to the buffet, and enjoyed themselves much in the same way as if they had been school-children surreptitiously breaking loose from an assembly of grown-ups.

1909, Archibald Marshall [pseudonym; Arthur Hammond Marshall], “A Court Ball”, in The Squire’s Daughter, New York, N.Y.: Dodd, Mead and Company, published 1919, page 9