Work-shy describes a person who avoids work because they simply do not want to do it. It is not about being tired, or ill, or unable to find a job — it is an accusation of laziness, and specifically of dodging effort that is rightly yours.

The 'shy' part is doing something unusual here. It does not mean quiet or nervous; in this old pattern, -shy means 'afraid of and keeping away from', the way a horse shies away from a snake. Compare 'camera-shy' (hates being photographed) and 'gun-shy' (nervous about something after a bad experience). So a work-shy person shrinks away from work the way a shy animal shrinks from a hand.

It is British far more than American, and it lives mostly in newspapers, politics, and complaining. Politicians and tabloids in the UK have used it for decades in the phrase 'work-shy scroungers' to attack people receiving unemployment benefits — so the word now carries real political heat. It sounds unkind and old-fashioned, and using it says something about you as well as about the person you're describing.

Usually it goes in front of a noun (a work-shy colleague) or after 'be' (he's work-shy). It keeps its hyphen most of the time.