It has passed into our language from the Arabic word "jihad". The word jihad is derived from the Arabic word 'cehd'. Cehd means “to use all the means necessary to achieve a goal”. From this point of view, wars made in the name of Islam can also be called jihad because they aim to spread the religion.
In Islamic literature, jihad means "striving, struggling against the enemies of Islam (non-Muslims), and spreading the requirements of religion and the Qur'an to those around them".
Source: Turkish Religious Foundation/Islamic Encyclopedia, TDK