What is the meaning of oppose in hindi?

Right then. The most common phrase for 'oppose' in Hindi is विरोध करना (virodh karna).

'Virodh' literally means opposition or protest. The word 'karna' simply means 'to do'. So, you are essentially saying "to do opposition".

You can also use the phrase किसी के ख़िलाफ़ होना (kisi ke khilaaf hona). This translates more closely to "to be against someone or something". Both are used all the time and get the meaning across perfectly. For example, "I oppose the decision" would be "मैं इस फ़ैसले का विरोध करता हूँ" (Main is faisle ka virodh karta hoon).

Hope that clears it up for you.