Green’s Dictionary of Slang

pipe n.2

[pipe v.3 (1)]

1. [mid-19C+] a glance, a look (at).

2. an identification.

3. [1960s] a dream.

In phrases

do a pipe (v.)

[1910s] (Aus. und.) keep a lookout.

have a pipe (v.)

[1900s–80s] to glance at.

lay pipes (v.)

[1910s] to survey, to reconnoitre.

on the pipe

[mid-19C] (UK Und.) keeping a lookout; conducting a surveillance.