A respectful, somewhat dated term for one's own or someone else's mother. Often used in historical or formal contexts; in modern casual speech, お母さん is more common.
Where is your honored mother?
In period dramas, samurai often address their mothers as 母上.
Compound of 母 (はは, 'mother') and 上 (うえ, 'above'), an honorific suffix. The reading ははうえ reflects the older pronunciation of 上 as うえ.