indorsement vs signature

indorsement and signature both are nouns.

Word	Noun	Adjective	Verb	Adverb
indorsement	Yes	No	No	No
signature	Yes	No	No	No

As nouns, signature is a hypernym of indorsement; that is, signature is a word with a broader meaning than indorsement:

indorsement (noun)	signature (noun)
the act of endorsing	a distinguishing style
formal and explicit approval	your name written in your own handwriting
a promotional statement (as found on the dust jackets of books)	a sheet with several pages printed on it; it folds to page size and is bound with other signatures to form a book
a speech seconding a motion	the sharps or flats that follow the clef and indicate the key
a signature that validates something	a melody used to identify a performer or a dance band or radio/tv program