The word "Jihaad" (جهاد) in Arabic has a number of meanings:
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1) Fighting in the cause of Allaah
Q5: 54. O you who believe! Whoever from among you turns back from his religion (Islam), Allaah will bring a people whom He will love and they will love Him; humble towards the believers, stern towards the disbelievers, fighting in the Way of Allaah, and never fear of the blame of the blamers. That is the Grace of Allaah which He bestows on whom He wills. And Allaah is All-Sufficient for His creatures’ needs, All-Knower.
2) Spending one's money and spending one's being
Q4:95. Not equal are those of the believers who sit (at home), except those who are disabled (by injury or are blind or lame), and those who strive hard and fight in the Cause of Allaah with their wealth and their lives. Allaah has preferred in grades those who strive hard and fight with their wealth and their lives above those who sit (at home). Unto each, Allaah has promised good (Paradise), but Allaah has preferred those who strive hard and fight, above those who sit (at home) by a huge reward.
3) Enduring and being patient
Q47:31. And surely, We (Allaah) shall try you (believers) till We establish those who strive hard (in response to the divine test) and those who are patient; and We shall put to the test your words and deeds (i.e. to draw the line between the one who is a liar, and the one who is truthful).
4) Opposing firmly
Q9:73. O Prophet (Muhammad)! Strive hard against the disbelievers and the hypocrites, and be harsh against them! Their abode is Hell; and worst indeed is that destination.
5) Showing of obedience to Allaah
Q29: 6. And whosoever strives, he strives only for himself. Verily, Allaah stands not in need of any of the ‘Âlamîn (mankind, jinn, and all that exists).
6) Apply the provisions of Sharia (Divine Law)
Q66:9. O Prophet (Muhammad)! Strive hard against the disbelievers and the hypocrites, and be severe against them; their abode will be Hell, and worst indeed is that destination.
7) Imposing forcefully
Q29:8. And We (Allaah) have enjoined on man to be good and dutiful to his parents; but if they strive to make you join in worship as a partner with Me (Allaah) anything of which you have no knowledge, then obey them not. Unto Me is your return and I shall tell you what you used to do.
8) Seeking obedience to Allaah in different ways
Q29:69. As for those who strive hard in Us (Our Cause), We will surely guide them to Our Paths (i.e. Allaah’s religion - Islamic Monotheism). And verily, Allaah is with the Muhsinûn (good doers)."
9) Conveying the divine message through utmost endeavor
Q25: 52. So obey not the disbelievers, but strive against them (by preaching) with the utmost endeavor with it (the Quraan).
10) Dutifulness and care towards one's parents, people
Hadeeth: A man asked the Prophet, 'Can I go on jihad?'
The Prophet asked, 'Are your parents alive?'
The man answered, 'Yes.'