plumb

Concise Oxford English Dictionary © 2008 Oxford University Press:
plumb1

▶verb

• 1 measure (the depth of a body of water).

• 2 explore or experience fully or to extremes: she had plumbed the depths of depravity.

• 3 test (an upright surface) to determine the vertical.

▶noun a lead ball or other heavy object attached to a line for finding the depth of water or determining the vertical on an upright surface. ▶adverb

• 1 informal exactly: plumb in the centre.

• 2 N. Amer. extremely or completely: they must be plumb crazy.

• 3 archaic vertically.

▶adjective

• 1 vertical.

• 2 Cricket (of the wicket) level; true.

word history: The word plumb entered Middle English via Old French, from the Latin plumbum ‘lead’. It shares this root with the words plumber, plummet, and aplomb. A plumber was originally a tradesman who worked with lead, which was formerly used for water pipes. In the Middle Ages plummet denoted a plumb or plumb line; its use as a verb to mean ‘fall rapidly’ is a 20th-century development. Aplomb entered English from the French phrase à plomb ‘according to a plummet’: it originally meant ‘perpendicularity, steadiness’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
plumb2

▶verb (plumb something in) Brit. install a bath, washing machine, etc. and connect it to water and drainage pipes.

■ install and connect pipes in (a building or room).

– origin C19: back-form. from plumber.