The term 'resinous substance' refers to a type of material that is composed of a sticky, viscous liquid. The two crossword solutions for this term are LAC and PITCH. LAC is a type of resin secreted by certain insects, while PITCH is a dark, viscous material derived from the distillation of coal tar or wood tar. Both of these substances are used in a variety of applications, such as adhesives, sealants, and waterproofing agents.