Immature female horse, (under 3 or 4 years of age).

Young horse mare (female.)

Female horse 4 years old or younger.

(noun) A young female centaur.

Female horse 4 years and under that has never produced a foal.

a female horse under the age of four.

young (under 4 years) female horse

A teenager female horse.

A female horse up to 4 years of age.

(animal science) A female horse less than three years old.

a female baby foal

a female baby horse and used often in photo shoots to get pictures of a breeds baby horses

A female horse under the age of 4

Female horse aged four or less.

Female horse under five years old.

Female horse (3 years and under).

A female horse about to the age of 4.

A female 3 years of age or less.

a female horse until she is fully grown, which is generally taken as four years of age

a female horse up to and including the age of 4.

Female horse four-years-old or younger.

A female horse whose age is 4 or under.

a female horse under 5 years of age

Female horse under three years of age.

A female horse aged three or under.

A female horse three years of age or younger.

a young female horse who has not yet had a foal between the ages of birth and 4 years.

A female horse is called a FILLY up until her fourth birthday when she becomes a MARE.

A young female horse aged 3 years or younger.

a female horse under one year of age

Female horse, 3 years old or less

A female horse less than 5 years old.

A female horse, age three or under.

A young female horse not more than four years of age.

a young female horse under three years old.

Female horse up to three years of age

Female horse under four years old

A female horse up to five years of age.

A female horse, under five years of age. At five they are then called mares.

A female horse under 4 years old

Female horse up to four years old

A female horse under the age of 3 years.

Female horse 4 years old and younger.

A filly is a young female horse, too young to be called a mare. There are several specific definitions in use.