Any of several kinds of speedwell (genus Veronica), which grow in rocky habitats; especially V. fruticans, which has bright blue flowers and is found in mountainous regions of Europe.
Origin
Early 18th century.
Definition of rock speedwell in US English:
rock speedwell
noun
Any of several kinds of speedwell (genus Veronica), which grow in rocky habitats; especially V. fruticans, which has bright blue flowers and is found in mountainous regions of Europe.