Sentence:  Tangled in the bushes we found a rusty length of <WSD>drainpipe</WSD>; we fastened it to the tree and made a kind of big nest above in the branches and spent a lot of time scrambling up and down the tree into the nest and hollering secret coded messages into the <WSD>drainpipe</WSD> to a comrade below. 
Meaning of the word marked with <WSD> tags:  The type of pipe that is used to construct a drainpipe.