pylon.
1. Portal of an Ancient Egyptian temple composed of two huge battered towers, usually decorated with bas-relief sculptured figures and hieroglyphs, flanking a lower framed gateway which, like the towers, was crowned by a cavetto or gorge-cornice. The towers had the corners finished with torus mouldings that were continued horizontally at the tops of the battered walls under the gorge-cornices. Some authorities use the terms pylon, propylon, pylône for the gateway, but others prefer pylon for the gateway and propyla for the towers. A pylon-form resembles one of the towers, and indeed the term pylon is now usually given to the towers, following the precedent set by the editors of the Description de l'Égypte (1820s). Pylon-forms (often found in C19 chimney-pots) lent themselves to the towers of suspension-bridges, such as Brunel's structure over the gorge at Clifton, Bristol (1831–64), and the battered section was widely employed in C19 dams and retaining-walls.

2. Tall structure erected as a support, especially a lattice-work metal tower to carry overhead electricity-lines.

3. Tall structure or pillar (left) Typical Egyptian pylon-form, with torus moulding, and simple cornice. (right) The form as an aedicule or door case. used either as an eye-catcher or as a marker for a boundary.

Bibliography

J. Curl (1994);
Cruickshank (ed.) (1996);
Gwilt (1903);
Lloyd & and Müller (1986);
Jane Turner (1986)

py·lon / ˈpīˌlän; -lən/ • n. an upright structure that is used for support or for navigational guidance, in particular: ∎  (also electricity pylon) a tower used for carrying power lines high above the ground. ∎  a pillarlike structure on the wing of an aircraft used for carrying an engine, weapon, fuel tank, or other load. ∎  a tower or post marking a path for light aircraft, cars, or other vehicles, esp. in racing. ∎  a monumental gateway to an ancient Egyptian temple formed by two truncated pyramidal towers.

pylon a monumental gateway to an ancient Egyptian temple formed by two truncated pyramidal towers.
In the early 20th century, the term was extended to cover a tall tower-like structure used for carrying electricity cables high above the ground; the word may be used (as in Pylon Poets) to designate those poets of the 1930s (chiefly W. H. Auden, C. Day Lewis, Louis MacNeice, and Stephen Spender) who used industrial scenes and imagery as themes of their poetry, after Spender's poem The Pylons (1933).

The word comes (in the early 19th century) from Greek pulōn, from pulē ‘gate’.

pylon (archit.) gateway XIX; tower, mast, etc. marking a course, supporting a span of wire. etc. XX. — Gr. pulṓn, f. púlē gate.