Pylon \Py"lon\, n.

1. A tower, commonly of steelwork, for supporting either end of a wire, as for a telegraph line, over a long span.

2. (A["e]ronautics)
   (a) Formerly, a starting derrick (the use of which is now abandoned) for an a["e]roplane.
   (b) A post, tower, or the like, as on an a["e]rodrome, or flying ground, serving to bound or mark a prescribed course of flight.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Pylon \Py"lon\, n. [NL., fr. Gr. ? a gateway.]


   (a) A low tower, having a truncated pyramidal form, and flanking an ancient Egyptian gateway.

Massive pylons adorned with obelisks in front. --J. W. Draper.
   (b) An Egyptian gateway to a large building (with or without flanking towers).

Source: Webster's Revised Unabridged Dictionary (1913)