1. Artfully dextrous in performing things secretly, and escaping observation or detection; usually implying some degree of meanness; artfully cunning; applied to persons; as a sly man or boy.
2. Done with artful and dextrous secrecy; as a sly trick.
3. Marked with artful secrecy; as sly circumspection.
4. Secret; concealed. Envy works in a sly imperceptible manner.
SLY'-BOOTS, noun A sly cunning or waggish person.