Sentence:  Finally, all men saw that astronomical knowledge lied not, and they awaited the comet. Its approach was not, at first, seemingly rapid; nor was its appearance of very unusual character. It was of a dull red, and had little perceptible <WSD>train</WSD>. 
Meaning of the word marked with <WSD> tags:  A transient trail of glowing ions behind a large meteor as it falls through the atmosphere.