わたしはドアをしめます。 I close the door. わたしはふくをぬぎます。 I take off clothes.

As dan said, the most common meaning of the verb しめる is 'to close' (in this case written 閉める) but it also has a different meaning: 'to tie / fasten' (written 締める in this case), like in シートベルトを締める - "to fasten seatbelt". So I guess in some contexts these two verbs could be treated as a pair of antonyms, e.g. ネクタイを締める／ネクタイを脱ぐ - "to tie a necktie" / "to untie a necktie" (I'm not sure if the latter is a 100% proper Japanese but uncle Google says they use it ;-) ).