Used on signs to indicate that entry into the area where the sign is displayed is forbidden.

Acronym of no observed effect level.

(anatomy, immunology) Each of the small oval bodies of the lymphatic system, distributed along the lymphatic vessels, that are clustered in the armpits, groin, neck, chest and abdomen. They act as filters, with an internal honeycomb of connective tissue filled with lymphocytes and macrophages that collect and destroy bacteria, viruses and foreign matter from lymph. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes.

A note or notation made in a side margin. / A minor related mention, made as an aside, or afterthought.

(idiomatic) Not exceptional; not noteworthy or especially good.

Having a flattened beak or snout.

of, or relating to non-Euclidean geometry

(geometry) Any system of geometry not based on the set of axioms of Euclidean geometry, which is based on the three-dimensional space of common experience.

(set theory) Of a set, containing at least one element; not the empty set.

A signal or process with a frequency spectrum such that the spectral energy density is proportional to the reciprocal of the frequency (1/f).