Wiktionary
a. 1 Separate from the main course. 2 supplementary or in addition to one's usual job or income. 3 Additional, surreptitious; often with a connotation of dishonesty or illegality.
WordNet
adv. without official authorization; "he had made some money on the side" [syn: unofficially]
Usage examples of "on the side".
We cannot at present pursue this subject further than to observe that from this negative intention are to be deduced all the advantages and all the stronger forms of combat which are on the side of the Defensive, and in which that philosophical-dynamic law which exists between the greatness and the certainty of success is realised.
Now it is known by experience, that the losses in physical forces in the course of a battle seldom present a great difference between victor and vanquished respectively, often none at all, sometimes even one bearing an inverse relation to the result, and that the most decisive losses on the side of the vanquished only commence with the retreat, that is, those which the conqueror does not share with him.
The moral effects resulting from the issue of a great battle are greater on the side of the conquered than on that of the conqueror: they lead to greater losses in physical force, which then in turn react on the moral element, and so they go on mutually supporting and intensifying each other.
He reflected that it was rather fun, this time, being on the side of the devil.
Joe about who I really was, but standing on the side of the parkway, it was suddenly abundantly clear to me that our relationship was doomed.
When we enquire by what means this wonder is effected, we shall find, that, as FORCE is always on the side of the governed, the governors have nothing to support them but opinion.