Adjective: three-year-old- Three years of age
"The three-year-old girl was excited to start preschool"
Noun: three year old- A racehorse that is three years old
"The three year old was favoured to win the Kentucky Derby";
- three-year-old horse
Derived forms: three year olds
See also: immature, young
Type of: bangtail [US, informal], neddy [Austral, informal], pony [informal], race horse, racehorse