cleistogamy

As a noun cleistogamy

is (botany) the production of flowers which do not open, and are self-fertilized in the bud.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between cleistogamy and dichogamy

is that cleistogamy is (botany) the production of flowers which do not open, and are self-fertilized in the bud while dichogamy is (biology) the condition in which an organism changes sex during its lifetime.