"Deculture" (pronounced de-kult-cha) is a Zentradei expression of shock and surprise. In the early days of the Zentradi/human conflict it was a negative term used often by the Zentradis to denote their shock and disgust at the human-only concepts of culture, music, love and sex. For instance, in the movie Macross: Do You Remember Love? Zentradis reacted with a surprised and disgusted "Yak Deculture!" when they saw a kiss for the first time.

However, since the war ended and Zentradis became assimilated into human culture the meaning of the word started to shift. Zentradis have come to love those very things they used to see as alien and deplorable, so the word "deculture" started to get a more positive connotation of pleasant surprise that is commonly used by non-Zentradis as well. For instance in the series Macross Frontier (set 47 years after the events of Do You Remember Love?) Ranka Lee sings the theme song for the Nyan Cafe:

Haochii rai rai, Meikuunyan, Nyan-nyan, nyan-nyan Nihao-nyan, Gojyasu! Derishasu! Deculture!!!! (Good Eats, come, come, Pretty Girls too! meow meow meow meow Hello meow Gorgeous! Delicious! Deculture!)

The tone of the song and usage makes it clear that it now means something along the lines of "Awesome!" or "No way!"