Aspects are not always easy to understand
Aspects are not always easy to understand and to apply a useful meaning to them that is consistent for any combination of planets involved. That is because the nature of the planets in an aspectual relationship can modify the typical mainstream keyword meaning for an aspect.
If we consider a conjunction between Sun and Jupiter we get impressions of bright, happy, cheerful, optimistic, luck, good fortune, expansive visions, etc. In a general sense we see these two as being able to work together. On the other hand, if Saturn and Mars are conjunct each other we have a tug-of-war view of how there energies are expressed --stop and go, force or restraint, anger versus stoicism, movement or stability, alive or dead, etc. In this case the energies or expression of the two planets constantly undermine each other.
So what definition of a conjunction would you use? Symbols tend to express themselves at several levels, in as many ways as possible. So, its possible to see Mars-Saturn as also meaning focused action, restrained force, cautious progress, brutal agression, harsh opinions -- these "definitions" combine the planet's meanings into a singular sense, while the first definitions were "either or" statements.
Conjunctions can be the toughest aspect to understand.
Would it surprise you to know that I believe that I do not use a consistent meaning for any aspect, that I often take a fluid approach depending upon the nature of the chart. We need rules to start off with, we later refine those rules, then we learn to bend them -- and at some point we sort of forget all about them. Its a process of change that occurs as we learn more about astrology. We start off by knowing a little about a lot. That changes so that we know a lot about a lot. Then we get to a point where we know a lot about little. Then we sort of know everything and nothing at the same time.
I'm not playing with your head. I'm trying to suggest that we change as what we know increases in volume, then we change more as what we know increases in complexity, and we move to/towards a point where we know enough to be flexible and seemingly to change the rules or forget the rules or act like we are intuitive. So, given all of this, I'll offer some aspect meanings which may or may not be useful and which I, myself, may or may not use.
Conjunction: An intensifying of two/more planetary expressions in that they may blend or bend each other.
Opposition: A separative expression of the planet's meanings when stressed, a projective force when one planet is supported more than the other, a negotiated expression when both planet's expressions need an outlet, otherwise a pull-pull, seeking to re-balance expressional values when other conditions don't seem to apply.
Square: Most often a challenging aspect wherein each planet's expression seeks to divert, dislodge or slice into the other's level of influnence.
Trine: These two planets do not challenge or separate their expression but instead use their particular energies to support a "movement" from one form of expression to another. When a grand-trine is involved, it acts like a motor that just runs and runs, the subject goes from one form of expression to another to another and then repeats the cycle like it was a compulsive habit.
Once we get to the minor aspects we find both variations of the major aspects as well as nuances being (often but not always) expressed.
Sextile: Nat an ease of application and energy like the trine, but certainly an ease of communication and understanding and movement.
Semi-square and sesquiquadrate: Both act like a combination of the square and the conjunction to some degree. The semi-square tends to find one planet trying to undercut or diminish the expression of the other. The sesquiquadrate tends to make adjustments in terms of how the two planets can work together rather than fight each other. Its a forced cooperation that permits each to work in cycles; first one than the other.
The inconjunct aspect often results in the two planets making changes in small increments rather than go to into a whole cooperation mode or to do a "first me, then you" type of approach.
The semi-sextile is, at best (in my opinion) a suggestion or prompting for making a change -- but it needs additional input from other forces such as one planet also having another aspect to help it along.
Hope this helps. Dave