What does "second estate" mean?

The caste of nobility in medieval and early modern society, and in particular in France prior to 1789, as distinct from the clergy and the commoners.

What is a synonym for "second estate"?

Common synonyms include: lords temporal.

noun

noun ·Rare ·Advanced level

Noun

1
The caste of nobility in medieval and early modern society, and in particular in France prior to 1789, as distinct from the clergy and the commoners.
2
the nobility in France and the peerage in Britain wordnet
3
The House of Lords.

See etymology at fourth estate.