Meaning
Striving and exertion in God's cause; primarily the moral and spiritual struggle against the self's lower nature, and secondarily struggle against injustice and oppression.
Literally: Striving, exertion (from jahada, to strive).
How Iqbal uses it
Iqbal foregrounds jihaad above all as the greater inner striving, the ceaseless moral effort by which the self is perfected and the will steeled against ease. In the social sphere it becomes for him the struggle against tyranny and the slothful inertia that keeps a people enslaved.
See it in the verse