A definition

Psychological safety is a shared belief held by members of a team that the team is safe for interpersonal risk taking without fear of repercussion. People feel able to speak up when needed, with relevant ideas, questions, or concerns. without fear of humiliation, rejection or not being liked.

Interpersonal risk includes being able to;
Speak up, ask questions, mention concerns
Admit mistakes and vulnerability
Talk about a sensitive topic openly and disagree
Be authentic and ‘bring their full selves to work’

Amy Edmondson The Fearless Organisation

Teams with it have,

Curiosity to ask questions and think big
Trust between employees
Open-mindedness to change, perspectives, take on new ideas.
Self-motivation and a sense of purpose
Resilience in confronting and overcoming conflict
B Frederikson

Teams without it

Employees don’t ask many questions during meetings.
Employees don’t feel comfortable owning up to mistakes
The team avoids difficult conversations and hot-button topics.
Executives and team leaders tend to dominate meeting discussions.
There are hardly any disagreements or differing points of view.
The Predictive Index

Resources
For a free organisational scan with the Fearless Organisation
Simon Sinek shares his definition in this short video
Amy Edmondson explains why its vital for genuine equality, diversity and inclusion