open-ended

adjective

1. not having fixed limits; unrestricted; broad: an open-ended discussion.
2. allowing for future changes, revisions, or additions: open-ended agreements.
3. having no fixed answer: an open-ended question.

adjective

1. without definite limits, as of duration or amountan open-ended contract
2. denoting a question, esp one on a questionnaire, that cannot be answered “yes”, “no”, or “don’t know”

adj.1825, from open (adj.) + end (n.).