noun

1. the act or position of one that sits, as for a portrait
2. a session or meeting, as of a court
3. a period of being seated at some activity to read a book in two sittings
4. 1. a brooding upon eggs, as by a hen
   2. the number of eggs upon which a hen sits for a single hatching
5. a space in which to be seated
6. one of two or more successive periods when a meal is served, as aboard a ship assigned to the second sitting

adjective

1. that sits; seated
2. in office a sitting president