noun · A coloring matter extracted from lichens, used in chemistry as an acid-base indicator.

我们将蓝色石蕊试纸浸入酸性溶液中，它会变红。

noun · A type of fruticose lichen commonly found in arctic and alpine regions, serving as food for reindeer.

石蕊是北极圈内驯鹿在冬天的主要食粮。