a : the system of beliefs and laws by which a country, state, or organization is governed
The state's constitution has strict rules about what tax money can be used for.
The right to free speech is guaranteed by the (U.S.) Constitution.
Members of the club have drafted a new constitution.
b : a document that describes this system
The state's original constitution is on display at the museum.
2 [count] : the physical health and condition of a person or animal
He has a robust/weak/tough constitution.
Only animals with strong constitutions are able to survive the island's harsh winters.
3 [noncount] formal : the form or structure of something
What is the molecular constitution of the chemical?