Actually it is questions such as this that I am really interested in, rather than intellectual arguments against all the silly superstitions. This is about how to enjoy life. And THAT, I think, is the ultimate question.

Contentment is to be at peace with yourself and your fellow man. In the end it is what all people seek, actually the only thing we seek. The real question is how to get there? My answer is to do an inventory of all your beliefs (and I mean ALL) and dump all your superstitions.

to have achieved all or most of your important goals of that time

To me it it means satisfied with what you have. Not wanting any more. But it doesn't mean your happy with what you have either.

I felt it and expressed it, but didn't 'think' of it as a concept. Thanks, Atheist, for this opportunity for an involved discussion.
This is how i tried to express it (apologies for posting the same poem again):

Contentment

imperceptible motion
of breathing
rising, falling
below a soft
deep
ripe red
cotton shawl

It's not about the things/people i need to live my life. That is 'satisfaction' when i have all i need.
It's not about my 'wants' either, when i want something i don't have, i call it 'desire'. When i have what i want, it's 'ecstasy'.

To me, contentment is not a state of mind but of consciousness- that's attained by some basic understanding of the vital link between one's individual self and the larger world. It does not leave me when i'm angry, sad or low energy.

What a strange kind of lovely bird.

The dictionary describes content as:
con·tent1
k?n?tent/Submit
adjective

1. in a state of peaceful happiness.
   "he seemed more content, less bitter"
   synonyms: contented, satisfied, pleased, gratified, fulfilled, happy, cheerful, glad; More
   verb

2. satisfy (someone).
   "nothing would content her"
   synonyms: satisfy, please
   noun

3. a state of satisfaction.
   "the greater part of the century was a time of content"

4. a member of the British House of Lords who votes for a particular motion.

Content to me means your needs, wants, and desires have been met and you no longer have to strive to attain them.

Most people have their own level of contentment but some are never content with what they have.

There is no answer to this question. Contentment is different for each person you ask. As evidence to this: I am most content when I am not content. What? There is nothing complicated about this. I feel the most comfortable and at rest when I'm busy chasing down some idea, struggling with my next novel, pressing to be heard in an engineering conference, trying to convince management that the ship can be built, etc.

So, what does it mean to be content?

Speaking only for myself, contentment is the quality of my baseline, day-to-day state of mind and being that doesn't entail wishing for things I don't have. My physical and emotional needs are met when I'm contented, even when there may be some manageable stresses and difficulties. I may strive for things, too, but that very well may fit in with my emotional need for growth or novelty. Happiness, I think, is an unsustainable state of mind that elevates us for a brief time from contentment to a stress-free, problem-free circumstance, e.g., on vacation, that allows our brain to feel significantly better than our baseline existence, but that will always normalize eventually.

Depends on who's using the words. The dictionary says they are close to the same.