1. verb "To spell a word". To arrange letters in the correct order to create words. English has a peculiarly esoteric and semi-phonetic system that creates a need for years of work before a given child can spell correctly, and even college graduates cannot spell many common words. The difficulty of English spelling gives rise to the phenomenons of spelling bees and spell checkers.
2. noun "To cast a spell". That which is done to enact magik. A word or set of words (or sometimes an action, set of actions, or actions and words together) that when spoken (or done) are supposed to have a supernatural effect.
3. verb "I'll spell you" To take over someone's task for them so that they can take a short break.
4. noun "Rest for a spell". A short amount of time, as in "stopping for a spell". Longer than a 'moment', but still indicating a temporary pause in a grander task or journey.