To express polite refusal. To slope downward; descend. To bend downward; droop. To degrade or lower oneself; condescend. To deteriorate gradually; fail. To sink, as the setting sun. To draw to a gradual close; wane. To refuse politely: I declined their offer of help. See Synonyms at refuse1. To cause to slope or bend downward. Grammar To inflect (a noun, a pronoun, or an adjective) for number and case. The process or result of declining, especially a gradual deterioration. A downward movement. The period when something approaches an end. A downward slope; a declivity. A disease that gradually weakens or wastes the body.