noun
family heirloom; trump card; last resort
Primarily used in the idiom 伝家の宝刀 (でんかのほうとう), meaning a treasured family sword passed down through generations, and figuratively a last-resort trump card or ultimate weapon. The standalone noun 伝家 is rare; the idiomatic usage dominates.
彼は伝家の宝刀を抜くことにした。
He decided to play his trump card.
この壺は我が家の伝家の品です。
This pot is a family heirloom of ours.
From 伝 (でん, 'transmit') + 家 (か, 'house/family'), literally 'something passed down in a family'. The figurative meaning comes from the idiom 伝家の宝刀, where a treasured sword becomes a symbol of a last resort.