expression, na-adjective
Describes something so impressive, beautiful, or exciting that it takes one's breath away. Often used for scenery, performances, or moments of great beauty or intensity.
その景色は息を呑むようだった。
The scenery was breathtaking.
息を呑むような美しさだ。
It's a breathtaking beauty.
息を呑む is a verb phrase meaning 'to gasp' or 'to hold one's breath' (in surprise or awe). 息を呑むよう is the adjectival form, describing something that causes that reaction.
From the verb phrase 息を呑む (to hold one's breath, to gasp) + よう (appearing, seeming). The expression figuratively describes something so striking that it makes one catch one's breath.