This is the 933rd most frequent Portuguese word.
matar
"To kill."
Here, the word 'matar' is used in its literal sense, meaning 'to kill', referring to ending the life of the insect.
Ele me disse que foi obrigado a matar aquele inseto.
He told me that he was forced to kill that insect.
In this slang usage, 'matar' means 'to fulfill' or 'to satiate', in this case targeting a need or urge, expressed figuratively.
Preciso de um café para matar minha sede.
I need some coffee to quench my thirst.
Here, the word 'matar' is used metaphorically to express intense feelings, such as making someone overwhelmingly curious.