To increase the amount or substance of: fatten one's bank account. (verb-transitive)
To grow fat or fatter.(verb-intransitive)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "fatten" in a sentence
"Since you're trying to "fatten" her up a little, I hope you don't benefit from the same."
"Insurance firms also fatten their bottom lines by denying more claims."
"The last 20% just says 'give private companies more money and fatten them up with profits while taking all regulations off so that they can abuse customers more.'"