This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means swell, so the verb version is to swell or to expand.

Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:

If someone comes up to you and says, "Hey it looks like you've really started to expand around the middle." Go ahead and say a big old, "F@#$ (ふく) you!" If someone is rude to you, dish it right back out. F@#$ that guy!