Bernard Lewis says that in the overwhelming majority of cases, "jihad" in Islam's core texts means military jihad

He writes on page 72 of his book The Political Language of Islam, that
...the overwhelming majority of classical theologians, jurists, and traditionalists [Muslim specialists in the Qur'an, hadiths, life of Muhammad, and Islamic law] ... understood the obligation of jihad in a military sense.
Lewis also writes, on page 31 of his book The Crisis of Islam, that
For most of the fourteen centuries of recorded Muslim history, jihad was most commonly interpreted to mean armed struggle for the defense or advancement of Muslim power.