giturumbuka : short form (without augment) of...
igiturūmbuka (ibi-)     4  class 4
singular: iki-,ic-
plural: ibi-,ivy-
  
sudden happening
giturūmbuka     adv    suddenly
 giturumbuka : Prefixless Present 4.class sing. of:
guturūmbuka (-turūmbutse)     v    to come suddenly, appear suddenly
happening    (sudden) igiturūmbuka
En-En dictionary 
sudden    (happening) igiturūmbuka
En-En dictionary 
suddenly    giturūmbuka
(as death or accident) bukumbi
(to come) guturūmbuka
(to happen) kwūbira
En-En dictionary