Definition of spell:
(n) :
words or a formula supposed to have
magical powers; a magical
incantation; a magical effect induced by an incantation or formula
"he cast a spell to cure warts."
(v) :
to comprise a word, as the letters "a", "n" and "d" spell "and"; to write or say the letters that form a word or part of a word
"this spells trouble."