Technically, the English name is a misunderstanding, being named after Lochan na Gaire, the 'little loch of the noisy sound', a loch to be found in the mountain's northeast corrie. Today the lochan is popularly called Lochnagar too. The summit itself is usually referred to as Cac Càrn Beag, meaning "small cairn of faeces" in Scottish Gaelic.
Beinn Chìochan (mountain of breasts) is an alternative Gaelic name.
The mountain's principal feature is a north-facing corrie around which most of the subsidiary tops as well as the main peak sit. The mountain is a Munro and is popular with hillwalkers at all times of the year. The most common ascent route is from Glen Muick. Care should be taken on the summit in poor visibility: the plateau has few obvious features and has steep cliffs on its northern edge.
The peak also lends its name to the poem Lachin y Gair (also known as Dark Lochnagar) by Lord Byron, and the song based on it.
Lochnagar experiences an Alpine Tundra Climate, with freezing, snowy winters and cold summers. The nearest UK Met Office weather station is at Braemar 6.6 miles (10.6 km) northwest. The yearly temperature range is usually between −6.6 °C (20.1 °F) and 9.4 °C (48.9 °F), but it can be slightly warmer and colder. January has the highest average frosts, despite February nights being colder; January has an average of 26.9 frost days, compared with 24.3 in February. There is the risk of a frost at any time of the year, even in July and August, when each month averages 1 air frost every 10 years.