"A breast-shaped hill is a hill in the shape of a breast," Wikipedia helpfully says in its titularly-titled article about breast-shaped hills. It goes on to list and describe mammorous mountains and hooterific hummocks in Africa, Antarctica, Asia, Europe, the Americas, and Oceania.
Breast-shaped hills are often connected with local ancestral veneration of the breast as a symbol of fertility and well-being. It is not uncommon for very old archaeological sites to be located in or below such hills, as on Samson, Isles of Scilly, where there are large ancient burial grounds both on the North Hill and South Hill, or Burrén and Burrena, Aragon, Spain, where two Iron Age Urnfield culture archaeological sites lie beneath the hills.
Many of the myths surrounding these mountains are ancient and enduring and some have been recorded in the oral literature or written texts; for example, in an unspecified location in Asia, there was a mountain known as "Breast Mountain" with a cave in which the Buddhist monk Bodhidharma (Da Mo) spent a long time in meditation.
"Mamelon" (from French "nipple") is a French name for a breast-shaped hillock. Fort Mamelon was a famous hillock fortified by the Russians and captured by the French as part of the Siege of Sevastopol during the Crimean War of the 1850s. The word "mamelon" is also used in volcanology to describe a particular rock formation of volcanic origin. The term was coined by the French explorer and naturalist Jean Baptiste Bory de Saint-Vincent.