A gusset is a triangular piece of fabric that is inserted into a seam to add width to a garment. Clothes that are too tight can have a gusset inserted at the centre back, sides seams or at the inside leg in the crotch area. Some tailors will have an insert at the inside leg that is not quite triangular, but has been added because the person has a large thigh.
Happy sewing
Judith aka genie
Posted in Clothes too tight - Let out, Clothing Alteration - General, Dresses and Gowns, Trousers | 
Tags: Let out trousers