The Collaborative International Dictionary of English v.0.48:
Pipeclay \Pipe"clay`\, v. t. 1. To whiten or clean with pipe clay, as a soldier's accouterments. [1913 Webster] 2. To clear off; as, to pipeclay accounts. [Slang, Eng.] [1913 Webster]WordNet (r) 3.0 (2006):
pipe-clay v 1: whiten or clean with pipe-clay; "pipe-clay leather"