(derogatory) A country or region regarded as under the control of the United States.

plural of first-chance exception

(physics) A spectrum produced by a diffraction grating whose adjacent slits are one wavelength apart.

plural of first-time buyer

(graph theory) A search algorithm that begins at the root node and explores all the neighboring nodes.

(idiomatic) A person or position that is formally of equal rank to others in a group, but nonetheless takes a leading role within that group.

Familiar with someone, such that one can address them by their first name. / (by extension, humorous) In regular contact with a person or organisation.

(mathematics) The time taken for a random walker to reach a specified target

(US, Army) A non-commissioned officer in the United States Army, ranking above a staff sergeant and below a master sergeant or first sergeant.

(law) A provision in a contract that permits a party to that contract or another named party to have an opportunity to purchase, use, or otherwise obtain a specified object before it is offered to any other party.