a more or less abrupt swelling, especially at the apex or base of a petiole or leaf sheath, often glandular and/or being the place where a plant responds to touch, gravity or light, in panicoid grasses a swollen region in the stem above the intercalary meristem - such a definition would also include stems of Chloranthaceae, Acanthaceae, Caryophyllaceae, Amaranthaceae, etc., cf. articulation.n