noun
ornamental garden stone; garden rock
A stone placed in a Japanese garden to create a natural, uncontrived look; often part of a rock arrangement.
日本庭園には、自然に見えるように捨て石が配置されている。
In Japanese gardens, ornamental stones are placed to look natural.
noun
sacrifice stone (in Go)
In the game of Go, a stone deliberately placed to be captured as part of a larger strategy.
プロの対局では、捨て石を使って相手の石を封じる手がよく見られる。
In professional Go games, you often see moves that use a sacrifice stone to seal in the opponent's stones.
noun
sacrifice (of oneself, one's career, etc.)
Metaphorical use, often in the pattern 〜に/となる, describing a person or thing willingly given up for a greater purpose.
彼は会社の再建のために、自ら捨て石となることを選んだ。
He chose to become a sacrifice for the company's reconstruction.
noun
foundation stone; riprap
Stones used as a base in construction or as riprap for erosion control; a more technical, literal sense.
護岸工事では、波の浸食を防ぐために捨て石が使われる。
In revetment work, riprap stones are used to prevent wave erosion.
捨て駒 is a sacrifice piece in shogi, while 捨て石 is a sacrifice stone in Go or a metaphorical sacrifice.
Compound of 捨て (stem of 捨てる, 'to throw away') + 石 ('stone'). The metaphorical sense derives from the idea of a stone that is deliberately discarded for a larger purpose.