Ectomorph are for the most part fragile, thin, lightly muscled, tall.
From the henleystandard.co.uk
A lovely effort from the occasionally awkward Essex ectomorph.
From the guardian.co.uk
What drives me crazy in the plus-size vs. ectomorph argument is that women who are in the middle weight classes are ignored.
From the stltoday.com
On the strength of such engaging fancies, Brooklyn-born Westlake, 41, a softspoken, owlish ectomorph who resembles most of his protagonists, has slipped into the front rank of popular crime writers.
From the time.com
More examples
A person with a thin body
Constitutional psychology is a theory, developed in the 1940s by American psychologist William Herbert Sheldon, associating body types with human temperament types.
Someone with a lean, only slightly muscular body; : Theoretical body type in which a person has a high metabolism. Such a person can easily maintain a low fat physique, but does not add muscle or body weight easily
Body Type Characterized by a light build and slight muscular development.
A body shape characterized by a narrow chest, narrow shoulders and long, thin muscles.
A person with an extreme body type typified by thin frame, long limbs and narrow features. People with a high degree of ectomorphy may suffer from physical fragility, sunken features and difficulty gaining fat or muscle. ...
Almost the same as a hard gainer, they are people who have a very fast metabolism and thus have a hard time gaining mass.
This is the body type that you were born with. The extreme ectomorph physique is a fragile and delicate one. The bones are light, joints are small and muscles are slight. The limbs are relatively long in proportion and the shoulders droop. ...
One of the 3 main human body types. It is characterized by a thin, linear appearance. They often possess narrow waist, hips and shoulders. The ectomorph also has a low body fat percentage.