Is the word biquíni the same in Brazilian and European Portuguese?

Yes

The spelling, meaning, and grammatical gender of the word "biquíni" are identical in both Brazilian and Continental Portuguese. The only difference between the two dialects is the pronunciation. In Brazilian Portuguese, the vowels are more open and the rhythm is syllable-timed, making the word sound more musical. In Continental Portuguese, the unstressed vowels tend to be more closed or even reduced, and the rhythm is more stress-timed, giving the word a more "clipped" or consonant-heavy sound.

Brazilian Portuguese Examples

1. Eu comprei um biquíni novo para a viagem. (I bought a new bikini for the trip.)
2. Ela está usando um biquíni azul muito bonito. (She is wearing a very beautiful blue bikini.)
3. Você viu o meu biquíni novo? (Did you see my new bikini?)
4. Esse biquíni é muito confortável para usar na praia. (This bikini is very comfortable to wear at the beach.)
5. Eu gosto muito desse biquíni que você comprou. (I like that bikini you bought a lot.)

Continental Portuguese Examples

1. Eu comprei um biquíni novo para a viagem. (I bought a new bikini for the trip.)
2. Ela está a usar um biquíni azul muito bonito. (She is wearing a very beautiful blue bikini.)
3. Viste o meu biquíni novo? (Did you see my new bikini?)
4. Este biquíni é muito confortável para usar na praia. (This bikini is very comfortable to use at the beach.)
5. Eu gosto muito deste biquíni que tu compraste. (I like this bikini that you bought a lot.)