In addition to the link to Thesaurus.com below, MS Word has a built-in thesaurus:
My keyword is vegetarian, and I need to brainstorm on some alternate terms, and then create 3 search strategies.
Alternate terms = herbivore / "no meat" / vegan
Three search strategy examples:
Ex #1.) (vegan or vegetarian) and "healthy eating"
Ex #2.) herbivore and eating and "no meat"
Ex #3.) vegetarian and "dietary considerations" and health