a woman's loose-fitting, dress- or skirt-length undergarment, suspended by shoulder straps ( full slip ) or by an elasticized waistband ( half slip ).  "a silk slip"  synonyms:	underskirt, petticoat  "a silk slip" Generally only used now if the dress or skirt has the potential to be see thru. Someone that age saying they are wearing a slip (which I don't believe from those pics) probably means they are from the Southern US.