¹ base noun

• the bottom or lowest part of something : the part on which something rests or is supported—usually singular —often used figuratively
• something (such as a group of people or things) that provides support for a place, business, etc.—usually singular
• a main ingredient to which other things are added to make something—usually singular

² base verb

• to have a particular place as the main place where a person works or lives or where a business operates —often used as (be) based

³ base adjective

• not honest or good
• having low quality and value