An intangible business asset which includes a cultivated reputation and consequential attraction and confidence of repeat customers and connections.
In many cases, goodwill is used interchangeably with the word reputation.
A claim for the tort of passing off usually includes an allegation that the defendant's actions depreciated the plaintiff's goodwill.
The Canadian Trade-marks Act (at canlii.org/ca/sta/t-13/), at ¶20 (extract only):
"The right of the owner of a registered trade-mark to its exclusive use shall be deemed to be infringed by a person not entitled to its use under this Act who sells, distributes or advertises wares or services in association with a confusing trade-mark or trade-name ... in such a manner as is not likely to have the effect of depreciating the value of the goodwill attaching to the trade-mark."