hit
The French word 'frapper' is a verb that means 'to hit'. It is used in a similar way to the English word 'hit'. For example, 'Il a frappé le ballon' means 'He hit the ball'. It can also be used in a more metaphorical sense, such as 'La nouvelle l'a frappé comme un coup de tonnerre' which means 'The news hit him like a thunderbolt'.
One should never hit a defenseless opponent.
Used here, 'frapper' describes the act of physically hitting or striking. In this context, it is a piece of advice emphasizing on moral conduct during conflicts, implying that taking advantage of someone's defenselessness for personal gain is ethically wrong and unacceptable.
The news of his death hit me like a punch.
In this sentence 'frapper' is used in a metaphorical sense, depicting the emotional impact that a piece of news can have, compared for effect to the physical force of a punch. It shows that the speaker was greatly affected by the mentioned news.
Lightning strikes the tower each year.
In this case, 'frapper' describes the action of lightning directly hitting or striking a tower. This statement could be used to illustrate how some places or objects are particularly prone to natural phenomena or events due to their location, material, or structure.