This tight little word can used either as a verb or a noun. As a verb, it means to raid or invade, but it can also be used in a less violent sense and mean to enter or try. As a noun, it simply describes that invasion or attempt.
Example (verb): Jill, a fully licensed interior design with over 20 years of experience, became infuriated when the general contractor forayed into her “territory,” undermining the legitimate choices she made for her clients and upsetting the scope of work.
Example (noun): Although he had worked on numerous hospitals and clinics during his career as an interior designer, Robert’s foray into the world of spa and hotel design was more challenging than he had expected.