IPA: /ˌɪndɪˈstrʌktəblɪ/
KK: /ˌɪndɪˈstrʌktəblɪ/
In a manner that cannot be destroyed or damaged.
The materials used in the construction of the building are designed to last indestructibly against natural disasters.
Indestructibly → It is formed from "in-" (meaning not), "destruct" (from Latin "destruere", meaning to tear down or destroy), and "-ibly" (meaning capable of being). The word "indestructibly" means capable of not being destroyed or unable to be torn down.
Think of 'not' ('in-') being able to 'tear down' ('destruere') something, which helps you remember that 'indestructibly' means something that cannot be destroyed.