[EricK]

LHO opens a weak 2; partner makes a simple suit overcall; RHO passes. What does a new suit bid by you show? How strong should it be? What's the minimum length? How forcing is it (eg non-forcing, 1RF, GF etc)? Does it deny support for partner?

I suppose there are potentially different scenarios where the answers might be different eg:
2 level overcall/2 level advance : (2♦) 2♥ (P) 2♠
2 level overcall/3 level advance below level of cue: eg (2♦) 2♥ (P) 3♣
2 level overcall/3 level advance above level of cue: eg (2♦) 2♠ (P) 3♥
3 level overcall/3 level advance below level of cue: eg (2♠) 3♣ (P) 3♥)
3 level overcall/3 level advance above level of cue: eg (2♦) 3♣ (P) 3♠

[rhm]

With an unpassed advancer forcing to game except that same suit rebid can be passed below game.

Rainer Herrmann

[Zelandakh]

I think the default is forcing to 3 of overcaller's suit. You can also play transfers for the advances above the cue (#3, #5) if that is part of your arsenal. The suit will usually be 5+ in length but might be shorter in, for example, a good balanced hand without neither fit nor a stopper in their suit.