I was preparing a little puzzle today for general instruction/amusement and I was describing a line as "forced" -- and now I wonder is forced the correct term? 

I use forced when there is only one "good" move. Like, yeah, you can do another move but you quickly lose a piece, etc. Is that 'forced'? Or is forced reserved only for those times when a move is very very directly compelled such as  -- when it is the only legal move or the only move that prevents a mate in one?

Is "only move" a synonym for "forced" or does it have a distinct meaning?

Thanks.

I'm interested in what the more experienced players have to say, but in my experience, forced does mean what you think: only one "good" or playable move in a position.  I've only heard "only move" though, when there is literally only one legal move that a player can make.

Forced probably means "only reasonable move"

A forced sequence is where you examine moves that leave the opponent only one reasonable reply on each of his turns

It's actually a little more complicated.

It is used in the sense you describe, or what heinzie calls "only reasonable move".

But, in puzzles and studies. these reasonable moves often lead to surprising or pretty losses anyway, so I would call it "Only apparantly reasonable move"

It is not logical or reasonable I think. These terms are too weak.
A move is forced when it is the only legal move. In the next diagram there is only one legal move black can do. (or resign but that isn't a move)

In the next diagram the queen is under attack. You can move the queen or take the rook. These moves are logical and reasonable.However, they aren't forced because you can play other moves as well. e.g. Nf6 is a legal move. No rule is against it.

Master players use 'forced' when the move is clearly the only reasonable move you can play and 'only move' when analysis shows that plausible alternatives are losing.

This is also how I understand it.  Both cases aren't necessarily "the only legal move" but they simply mean any alternative is considerably worse.  The difference is I hear "forced" in pseudo-analysis as in a post mortem, and "only move" in serious analysis such as in an article... as you said "only move" shows how seemingly reasonable alternatives actually lose while in most cases "forced" can be used without analysis because at face value there are no other reasonable alternatives.

I've also heard "only move" in terms of calling a position very difficult.  E.g. "black is probably equal here, but he'll be faced with finding many "only moves" ahead while white's play comes naturally."

And actually the informant symbols are use the same.  A box before a move means "only move" (if I remember correctly) and these are often not the only legal move.

In your 2nd diagram the black rook is trapped anyway so "Qxd6 forced" is probably too strong.  You usually see it in situations like these where there are many legal moves, but only 1 worth considering.

Qxb1 forced would be a correct annotation despite there being other legal moves.

I would also use the "forced" move, to describe "only reasonable move"

Not necessarily only move, but in a sense that you don't have a viable alternative.

Interesting point!