Constructive dismissal is when your employer changes your employment contract in a big way. It has to be such a drastic change that any reasonable person would think that the employer terminated the original contract and tried to impose a new one with different terms. 

The change could be in the form of a single, major unilateral change to the contract, such as a drastic change to job duties, hours of work, or compensation. 

It could also be in the form of a pattern of behaviour on the employer's part that suggests that they no longer intend to be bound by the employment contract, such as a pattern of bullying or harassment.

Constructive dismissal is sometimes called "disguised dismissal," “involuntary leaving,” or "quitting with cause" because the employee usually feels like they have no choice but to quit their job. 

If you think your employer has constructively dismissed you, contact Labour Standards as soon as possible or talk to an employment lawyer for legal advice.