[Bende]

In one strong club system, 1M shows a 4+suit, possibly with a longer minor, and 1♦ is used to show an unbalanced hand with either minor. How should one defend against this opening?

It would be possible to use a defense similar to that one uses against a common nebulous diamond but it doesn't seem to be the most effective. Specifically, using 2NT to show both minors is probably a bad idea.

[whereagles]

I used to have a scheme against that. It was something like...

Dbl = short in one minor, emphasis on majors. If LHO and pard both pass this, then diamonds become defined as our suit. Otherwise it remains as the cue bid, unless opener pulls to clubs.

1/2 level overcalls = usual natural stuff, including (1♦)-2♦.

2NT = club preempt or diamonds+major 2-suiter. If 2 suited, pull 3♣ response to 3♦.

3♣ = diamond preempt or clubs+major 2-suiter. If 2 suited, pull 3♦ to 3M.

3♦ = major 2 suiter.

Higher level overcalls = natural.

The 2 suited overcalls are intermediate or better (5 losers or less). If the 2 suiter is very strong, you pull into the level you wish to play. E.g.

(1♦) 2NT (pass) 3♣
(pass) 4♦

4♦ = "I can make 9-10 tricks on my own".

[jjbrr]

2♦ natural
2♥ both majors nf
3♦ both majors f

[gwnn]

1M natural, transfer advances starting at 1N
1NT natural, system on
2m natural, other minor=cuebid
2M weak
3m weak