There are various overcalls and other competitive bids to show two suited hands.
The Unusual 2NoTrump is one of the most popular:

"Unusual" for the Minors "Unusual" for Two Lowest Unbid Opener LHO 1 2N1 1 Clubs + Diamonds Opener LHO 1 2N1 1 Clubs + Hearts Opener LHO 1 2N1 1 Clubs + Diamonds Opener LHO 1 2N1 1 Diamonds + Hearts Opener LHO 1 2N1 1 Clubs + Diamonds Opener LHO 1 2N1 1 Clubs + Diamonds

Michael's Cuebid "Top and Bottom" Cuebid Opener LHO 1 21 1 Spades + Hearts Opener LHO 1 21 1 Spades + Diamonds

Opener LHO 1 21 1 Spades + Hearts Opener LHO 1 21 1 Hearts + Clubs

Opener	LHO	Responder
1	1	2

2: Limit raise or better in Opener's Suit

Opener LHO Responder 1 2N1 32 1 Clubs + Diamonds 2 Limit Raise or better Opener's Suit Responder xxx AQxxx xxx AJ Examples: Ax Axx xxx Qxxxx   AKx KQxx x AKxxx

Opener LHO Responder 1 21 22 1 Hearts + Spades 2 Limit Raise or better Opener's Suit Responder xxx xx KQTxx AJx Examples: xx xx KQTxx AKQJ   xx xx KQTxxx Axx

In each case above, Responder is "cuebidding" suits the opposition have shown, but which are not visible in the bidding diagram.
Some call those shown suits "invisible" (like ghosts that make noise: apparent for sound, yet invisible).
Cuebids of those suits are sometimes called "Invisible Cuebids".

Two-suited-showings allow for two "Invisible Cuebids".
Of those two possible Invisible Cuebids, one is Lower Ranking than the other.
Cuebidding the Lower Ranking suit is a limit raise or better.
Cuebidding the other suit (Higher Ranking) is Game Forcing.

Opener LHO Responder 1 2N1 32 1 Clubs + Diamonds 2 Forcing in the 4th Suit: Spades Responder AKxxx AQ xxx xxxx Examples: AKJxxx x xx KJxx   AQxxx Ax Axx xxx

Opener LHO Responder 1 21 22 1 Hearts + Spades 2 Forcing in the 4th Suit: Clubs Responder xx xx Axx AKQxxx Examples: xxxx A xxx AKQJx   AQ x KQT AJxxxxx

Cuebidding the Higher Ranking Suit shows 5+ of the fourth and last suit, Game Forcing.

Opener LHO Responder 1 2N1 32 1 Clubs + Diamonds 2 Non Forcing, To Play, Natural + Long Responder Jxxxxxxx Jxx xx Examples: AKxxxxx x xx xxx   AKQxxx xx xxx xx

Opener LHO Responder 1 21 32 1 Hearts + Spades 2 Non Forcing, To Play, Natural Responder xx x Kx Kxxxxxxx Examples: xx x xxx AKxxxxx   xx xx xxx AKQxxx

With 7+ cards in the 4th suit and only constructive values, one simply directly bids the 4th suit, NOT forcing,

Opener LHO Responder 1 2N1 X2 1 Clubs + Diamonds 2 Interest in Penalty Responder Axxx x Axxx Kxxx Examples: AJxx x xxx Kxxxx   AJx xx xx Kxxxxx

Opener LHO Responder 1 21 X2 1 Hearts + Spades 2 Interest in Penalty Responder Axxx Kxxx Axxx x Examples: Axxxx Kxx Axxx x   QJT8 Axx xx xxxxx

With 7+ cards in the 4th suit and only constructive values, one simply directly bids the 4th suit, NOT forcing,

Opener LHO Responder 1 2N1 32 1 Clubs + Diamonds 2 Constructive Raise Responder Axx Axxx xxxx xx Examples: KQJx Qxx Qxx xxx   AQxxx Jxxx xx xx

Opener LHO Responder 1 21 3 1 Hearts + Spades 2 Interest in Penalty Responder Axx xx Axxxx Jxx Examples: Kx xx Axxxx Qxxx   Axx xxx Jxxxxx Q

With a constructive raise (8 to 10 points), responder may simply directly raise.

An Alternative

Cuebidding the Higher Ranking Suit

Opener LHO Responder 1 2N1 32 1 Clubs + Diamonds 2 Like a "Negative Double" Responder AKxx AQ xxx xxxx Examples: AKJxxx x xx xxxx   AKQJ A xxxx xxxx

Opener LHO Responder 1 21 22 1 Hearts + Spades 2 Like a "Negative Double" Responder xx xx xxx AKQxxx Examples: xxx xx Kxxx AKQJ   xxx xxx KQT AJxx

Cuebidding the Higher Ranking Suit is like a Negative Double, showing 4+ cards in the unbid suit.
With 5+ cards in the 4th suit and sufficient points, one would simply make a forcing bid of the suit.
With 5+ cards in the 4th suit and only constructive values, one cuebids the higher ranking of the two suited showing.
With 5+ cards in the 4th suit, length and less than constructive values, one passes and can perhaps bid the suit later.