In “The Story of An Hour,” by Kate Chopin, the author uses this word in the following sentence.
“He had only taken the time to assure himself of its truth by a second telegram, and had hastened to forestall any less careful, less tender friend in bearing the sad message.”
According to the merriam-webster dictionary, it means:
“to exclude, hinder, or prevent by prior occupation or measures”
This would mean that he quickly prevented any other friends from deliver the message of the death of her husband.