Everyone's definition of success is different.

But one measure of it is how much freedom do you have?

Freedom of choice, time and financial freedom come with success. I think these are good goals for markers of success.

You can be wealthy and be time poor - which in that case, you're a slave to the thing that you have to be physically there to produce income. Should anything happen to you, the income stops.

I also know of law firm partners who earn $1-2 million dollars a year and have no assets besides their home and car (which despite their high incomes, still haven't been paid off!) Given their high income, you would call them a success - but they're lifestyle chasers. They have no assets to back them up should the main breadwinner lose his or her job, because they've thrown all their money into expensive cars, clothes, holidays, restaurants, and other random things which prevent them from paying off their homes and credit card debts (yes some have maxed out their credit cards while earning over a million dollars a year!)

For me, after 10 years of different "try and fail, until you succeed" answer on question 'What is " Success" ' ? is that success is not just reached goal or something similar, it is rather one step forward, it is state of mind.
State of mind that only winners can born with...

Success for me is sitting in my easy chair next to fire with a clear mind. My mind is clear because I have a healthy family, no debt, no mortgage, no credit card nothing. I also have enough in emergency funds to deal with most that god can send our way. It's a great feeling I am not a slave to things....

Knowing where you are going and what to do to get there generates confidence.
And this confidence is the fuel you need to succeed in life. Oyedepo

Success is achieving your happiness and contentment in life.

Success is....loving someone more than your own ego, and being loved equally back in return.

Nothing else, in the end, really matters.

Success is measured by finding someone you love to spend the rest of your life with, enjoying the good times, and sticking it out in the hard times.

Some other thoughts on success:

Action is the foundational key to all success. - Pablo Picasso

Always bear in mind that your own resolution to succeed is more important than any other. - Abraham Lincoln

Failure is success if we learn from it. - Malcolm Forbes

I don't know the key to success, but the key to failure is trying to please everybody. - Bill Cosby

I've failed over and over and over again in my life and that is why I succeed. - Michael Jordan

For me,
Success is achieving your plans/goals.
From being discontented to contented is Success.
The success means the completion of your goals and plans.