1to go to the bottom of a matter
2after all
3when all is said and done
4(in an interrogative sentence) finally
5outcome
6result
Examples
nà li那里jiū jìng究竟fā shēng发生le了shén me什么shì事？
那里究竟发生了什么事？
What exactly happened there?
究竟谁要负责？
Who exactly is responsible?
“但请告诉我们，您究竟为了什么杀了他？”“是为了爱情。”
"But tell us, just what did you kill him for?" "For love."