class

Concise Oxford English Dictionary © 2008 Oxford University Press:
class/klɑːs/

▶noun

• 1 a set or category of things having a property or feature in common and differentiated from others by kind or quality.

  ■ Biology a principal taxonomic grouping that ranks above order and below phylum or division, such as Mammalia.

  ■ Brit. a division of candidates according to merit in a university examination.

• 2 a system that divides members of a society into sets based on perceived social or economic status.

  ■ a social division based on economic or social status.

• 3 a group of students or pupils who are taught together.

  ■ a lesson.

  ■ chiefly N. Amer. all of the college or school students graduating in a particular year.

• 4 informal impressive stylishness in appearance or behaviour.

▶verb assign or regard as belonging to a particular category. ▶adjective informal stylish or excellent: he's a class player.

– phrases
class A (or B or C) drug Brit. an illegal narcotic drug classified as being of the most harmful and addictive (or a less harmful and addictive) kind.
class act informal a person or thing displaying impressive and stylish excellence.

– origin C16: from L. classis ‘a division of the Roman people, a grade, or a class of pupils’.