As this post is written in English [ok, apart from the bits which are in Double-Dutch] I am making the huge assumption that you understand the definition of many English words.
Words such as:
Simple, right? However, all these words – along with many others – are known as Contronyms, or Janus words.
That’s him, old two-face himself. Janus looks both forwards and backwards; he’s the Roman god of doorways, and the deity from whom we derive the name for January.
So, what has he got to do with the words in the list above? Well, each of these can mean the exact opposite of itself ;
You can dust furniture or dust a cake – in one you remove dust, in the other you add a dusting of sugar or some-such.
You can cleave something into two parts, or a couple can cleave together in marriage.
Something fast might be stuck fast or moving very quickly
A bus may have left the bus station or be left in it.
According to my in-depth research* [a quick search on Google!] there are 75 examples of contronyms in English, something for word-nerds to maybe use to spread confusion far and wide. Thanks, Janus!