The chronic inability to fall asleep or to remain asleep for an adequate length of time: Janet had insomniac problems regarding sleeping at night because she was constantly haunted by the fact that she couldn't pay back her loan debts.
2. A person who cannot sleep even when he or she is sleepy: Being an insomniac, and so not being able to go to sleep even when he tried to, Harvey decided to go to the bank and seek financial help to solve his payment problems because they were constantly on his mind.