Learner's definition of LONELY
[also more lonely; most lonely]
1 : sad from being apart from other people 2 : causing sad feelings that come from being apart from other people
It was lonely living out in the country.
She spent too many lonely nights at home.
She had a lonely childhood.
It's lonely at the top. [=powerful and successful people often have few friends]
3 : not visited by or traveled on by many people