(idiomatic) A joke that is understood or meant to be understood only by certain people who are aware of the details.

(US) Within the portions of Washington D.C., Maryland and Virginia encircled by Interstate 495. (The Washington Beltway)

(economics, banking) The amount of time it takes for the government or the central bank to respond to a shock in the economy.

(sports, chiefly racing) The lane or track nearest to the interior. / (figuratively) Any advantage.

(rugby) A player who is positioned between the fly-half and the outside centre

(US, idiomatic, baseball) Technical matters concerning baseball generally not apparent or of interest to spectators. / (US, idiomatic, by extension) Matters of interest only to insiders.

(idiomatic) A crime or other illicit action committed by or with the help of someone either employed by the victim or entrusted with access to the victim's affairs and premises.

(rugby) a back whose primary job is to create space for the outside backs outside him, i.e. the scrum-half, the fly-half and the inside centre.

Alternative form of inner diameter

plural of inside joke