0 past simple and past participle of decline
2 to refuse:
3 If a noun, pronoun, or adjective declines, it has different forms to show if it is the subject or object, etc. of a verb or if it is singular or plural, etc. If you decline such a word, you list its various forms:
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.