noun
unreasonable idea; illogical plan
Refers to a proposal, argument, or course of action that is forced, unreasonable, or doesn't hold up logically. Often used in discussions or negotiations.
その提案は無理筋だと思う。
I think that proposal is unreasonable.
彼の説明はどうも無理筋に感じる。
His explanation somehow feels illogical.
noun
illogical move (in shogi or go)
Original meaning; used in board games like shogi or go for a move that is strategically unsound or forced. Now less common than the general sense.
その手は無理筋で、すぐに反撃された。
That move was illogical and was immediately countered.
筋 means 'line', 'logic', or 'plot'. 無理筋 combines it with 無理 to mean an illogical line of reasoning.
Compound of 無理 (muri, 'unreasonable') and 筋 (suji, 'line of reasoning' or 'move'). Originally used in board games, later extended to general illogical arguments or plans.