grandchild    umwūzukuru
En-En dictionary 
umukēcuru (aba-)     1  class 1
singular: umu-
plural: aba-
  
old woman, widow (not very respectful term, can be used though by little children, or by grandchildren towards their grandmother)
umwuzukuru (ab-  1  class 1
singular: umu-
plural: aba-
  
grandchild
 grandchild found in: Kirundi II (Grammar)
chapter 53   Nouns of Relationship