The definition of indefinite is something that has no exact limits, is vague or that is not clearly defined.
Having no restrictions or controls:
Not fixed or known in advance:
Free from confinement or imprisonment; unfettered:
A method of execution whereby the person is dropped and suspended from a rope around the neck, resulting in death from severing of the spinal cord, strangulation, or other causes.
The definition of optional is available, but not required.
Find another word for open-ended. In this page you can discover 18 synonyms, antonyms, idiomatic expressions, and related words for open-ended, like: indefinite, exploratory, undetermined, unlimited, going-on, indeterminate, not restrained, without specified limits, continuing, either-or and ad hoc.