On one's feet; walking, jogging or running but not in a vehicle or on the back of an animal. [from 10th c.]
The pub's not far: let's go on foot.
(now rare, chiefly hunting) On the move; astir. [from 14th c.]
In progress or in preparation; active, in operation. [from 16th c.]
Source: en.wiktionary.orgCertainties are arrived at only on foot. Antonio Porchia
Tourism is sin, and travel on foot virtue. Werner Herzog
Hurrah for revolution and more cannon-shot A beggar upon horseback lashes a beggar on foot. Hurrah for revolution and cannon come again The beggars have changed places, but the lash goes on. William Butler Yeats
In my homeland I possess one hundred horses, yet if I go, I go on foot. Hindi Proverb
Sickness comes on horseback, but goes away on foot. Dutch Proverb
He who would go further than his horse, must alight and go on foot. German Proverb