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

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

(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.

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

plural of first-degree burn

(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.

(nautical) The first port that a vessel calls in at after the start of a voyage / (idiomatic) The first place to go to start a process.

(logic) A formal deductive system extended from propositional logic with the possibility to quantify over individuals of the domain of discourse.

plural of first-person shooter

(accounting, computing, business) Of or pertaining to any situation where the last to arrive is the first to go, or a data structure where the most recently added item is the first to be retrieved.