"Landscape orientation" refers to the way something is positioned horizontally, like a wide picture or a document that is wider than it is tall. Full definition
The power and volume controls are up top when held in landscape orientation for gaming and there's a 3.5 mm headphone jack on the bottom of the phone. (androidheadlines.com)
If a user records in landscape orientation with the headphone jack pointing right, the problem doesn't occur. (ibtimes.com)
They can also decide to use portrait or landscape orientation when viewing your page on a mobile platform. (entrepreneur.com)