This is the 10198th most frequent Japanese word.
閉め
"閉め" means "to close" (used for doors, windows, etc.).
Here, "閉め" indicates the action of closing something, specifically the door, by physically moving it to shut.
ドアを閉めてください。
Please close the door.
In this sentence, "閉める" is used in the infinitive form, referring to the act of closing something such as a window.
彼は窓を閉めるのを忘れました。
He forgot to close the window.
Here, "閉めました" implies securing something, here the door, using a key, showing its function in making something inaccessible.