Tamariki means: Children, or to be young.
Tamariki is the plural form of the word “tamaiti” (child). Generally, the distinction between takitahi (singular) and takitini (plural) nouns is made with the determiner: te/ngā, tōku/ōku, tētahi/ētahi.
However, there are a few words (all terms for people) which have unique forms for singular/plural. Of these, tamaiti/tamariki is even more unique because it’s the only one which doesn’t involve lengthening the vowel of the third-to-last vowel of the singular form:
Tamaiti and tamariki are believed to have emerged from “tama iti” (little child) and “tama ririki” (little children) becoming single words over time.