(1):
(v. t.) To write one's name, alone or with other words, upon the back of (a paper), for the purpose of transferring it, or to secure the payment of a /ote, draft, or the like; to guarantee the payment, fulfillment, performance, or validity of, or to certify something upon the back of (a check, draft, writ, warrant of arrest, etc.).
(2):
(v. t.) To give one's name or support to; to sanction; to aid by approval; to approve; as, to indorse an opinion.
(3):
(v. t.) To write upon the back or outside of a paper or letter, as a direction, heading, memorandum, or address.
(4):
(v. t.) To cover the back of; to load or burden.