Sentence:  "I've named my new noiseless aeroplane—Army Air Scout—I've named that <WSD>Silent Sam</WSD>. Wait until you hear it, or rather, don't hear it, and I think you'll agree with me. <WSD>Silent Sam</WSD> for Uncle Sam!" 
Meaning of the word marked with <WSD> tags:  A machine, device, etc. which operates without making noticeable sound.