Hanuman is pure devotion, humility and strength – He is the perfect being. But what does the term hanuman mean? It is believed that Hanuman got His name after being struck by the Vjara Ayudha (thunderbolt) of Indra on his jaw while attempting to snatch the Sun. Thus Hanuman means ‘one with a broken cheek.’
Some scholars and saints are also of the opinion that Hanuman means manifested existence of Supreme Consciousness that permeates in all.
Nu means ‘that which permeates’
Man means ‘manifested’
Some scholars have opinioned that this meaning is a bit farfetched.
But it is sure that the term Hanuman had its origin in the incident involving Indira and the thunderbolt. Because in Sanskrit ‘Hanu’ or ‘Han’ means ‘Jaw’ or ‘Cheek.’ It is believed that the thunderbolt used by Indra to stop Hanuman from touching the Sun hit Hanuman’s cheek and he got the name after this incident – ‘one with a broken cheek.’
Update - Pankaj Kumawat, a reader of the post, has send this shloka regarding the term Hanuman
Swayam ke maan ka hanan kar, yani swayam ke maan ki parwah Na kar, swami bhakti karana ka naam he Hanuman.