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

No

While the literal meaning of "altas" (the feminine plural of alto, meaning "high" or "tall") is the same in both dialects, the typical usage differs significantly. In Brazilian Portuguese, "altas" is frequently used as a colloquial intensifier to mean "great," "huge," "epic," or "intense" when describing events, situations, or feelings. In Portugal, this slang usage is much less common; a Portuguese person would typically use "grandes" or "enormes" to express the same idea of magnitude or greatness.

Brazilian Portuguese usage (Colloquial/Intense):

1. "Demos altas risadas no cinema." (We had great laughs at the cinema.)
2. "Ele se meteu em altas confusões ontem." (He got into some huge troubles yesterday.)
3. "Tivemos altas aventuras naquela viagem." (We had some epic adventures on that trip.)
4. "A festa de ontem foi alta!" (Yesterday's party was awesome/intense!)
5. "Ela tem altas ideias, às vezes." (She has some wild/crazy ideas, sometimes.)

Portuguese usage (Standard/Alternative):

1. "Demos grandes gargalhadas no cinema." (We had great laughs at the cinema.)
2. "Ele meteu-se em grandes confusões ontem." (He got into big troubles yesterday.)
3. "Tivemos grandes aventuras naquela viagem." (We had great adventures on that trip.)
4. "A festa de ontem foi enorme!" (Yesterday's party was huge/great!)
5. "Ela tem ideias muito loucas, às vezes." (She has very crazy ideas, sometimes.)