(underwater diving) A practitioner of free-diving.

(physics) The convection (carriage) of contents of a fluid, such as mass or (especially) heat, by means of currents induced in the fluid by a buoyancy force which is dependent on an acceleration (such as gravity) acting upon density changes in the fluid which are induced by heat.

Of, pertaining to, or produced by animals that are allowed to roam freely, rather than being confined indoors. / (figuratively) Allowed to move about outdoors without supervision.

(simile) Having no ties; completely free.

(group theory) A group that has a presentation without relators; equivalently, a free product of some number of copies of ℤ.

(mathematics) A group formed from others by concatenating their presentations (when those presentations are written with disjoint sets of generators).

Someone who obtains goods or services legally without paying. / (economics) One who obtains benefit from a public good without paying for it directly.

(idiomatic) Something obtained without any payment, obligation or effort.

(Incoterm) Meaning the seller incurs all costs of transportation up to a named carrier, after which the responsibility is with the buyer.

plural of free lunch