To Close Something
To Shut Something
transitive verb, ichidan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means closed so the verb vocab version is to close something.
閉める primarily means to shut something in a physical sense (often with a sliding or twisting motion), like when you close doors, windows, curtains, faucets, and so on. Additionally, it can also be used for closing shops, either for the day or permanently.
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:
When you want to close something, use a sheep (し). Sheep are famously good closers. Doors, windows, curtains, you name it. Sure, they'll bleat on and on about how they're not your personal closer, they have their own doors to close, and bah bah blah, but they secretly love having the chance to shut something for you.
ドアを閉める
to close the door
戸を閉める
to close the sliding door
店を閉める
to close the shop
フタを閉める
to close the lid
寒いから、ドア閉めるね！
It's cold, so I'll close the door, okay?
この店、閉めることになったんだ。
This shop is closing down.
ちゃんとフタを閉めておかないと、虫が入るかもしれないよ！
If you don't close the lid properly, bugs might get in!
旦那がペットボトルのキャップを閉める時、キツく締めすぎるのが嫌です。
I hate when my husband twists the caps back on plastic bottles really tightly.