Green’s Dictionary of Slang

lamp v.2

[lamp n.1 ]

1. [late 19C+] (orig. US, also lam, lamp up) to look at, to assess visually.

2. [1950s+] to consider, to think about [the image is of watching other people].

3. [1980s+] (US black/campus) to loiter, to ‘hang out’, to relax while others panic.