a closure, e.g. a strip of paper over the cork or cap of a bottle or jar, or a wax seal on a document, that must be broken in order to give access, and so when unbroken guarantees that the item so closed has not been opened or tampered with

a tight and effective closure, e.g. against the passage of air, water, etc

the water in a trap¹ (water-filled bend) in a pipe that prevents foul-smelling gases coming out of the pipe

something that confirms, ratifies, or makes secure; a guarantee or assurance

a seal of authenticity

an emblem or word impressed or stamped on a document as a mark of authenticity

a device used to impress such a word or emblem, e.g. on wax or moist clay

a disc, esp of wax, bearing such an impression

an ornamental adhesive stamp that may be used to close a letter or package

to close (something) so as to prevent anything getting in or out, esp to make it airtight or watertight

to close (a document, envelope, bottle, etc), with or without a seal, e.g. to prevent anybody opening it or tampering with the contents

to roast the outer surface of (meat) very rapidly and briefly so that the meat's juices remain in the meat when it is cooking

to cover (something porous, e.g. a plaster wall) with a coating of a nonporous substance

to fix (something) in position or close breaks in it with a filling, e.g. of plaster

to stick (one thing) fast to another

But ah! she gave me never a look, for her eyes were sealed to the holy book — Matthew Arnold

to set or affix an authenticating seal to (e.g.something such as a document)

to authenticate or ratify (something)

to mark (something) with a stamp or seal, e.g. as evidence of size, weight, capacity, or quality