Petticoat \Pet"ti*coat\, n. (Zo["o]l.) [Petty + coat.] A loose under-garment worn by women, and covering the body below the waist. {Petticoat government}, government by women, whether in politics or domestic affairs. [Colloq.] {Petticoat pipe} (Locomotives), a short, flaring pipe surrounding the blast nozzle in the smoke box, to equalize the draft.