1. Na-adjective (keiyodoshi), Noun which may take the genitive case particle 'no'

   sudden; abrupt; unexpected; immediate

   Usually written using kana aloneocc. written 遽か

   にわか仕込みの知識ではその問題は解けなかった。

2. Prefix, Na-adjective (keiyodoshi)

   improvised; hasty; impromptu; offhand

   Usually written using kana alone

3. Noun

   impromptu skit

   Abbreviationocc. written 仁輪加 or 仁和加see 俄狂言

4. bandwagon fan; fair-weather fan

   AbbreviationSlangUsually written using kana alonesee にわかファン

Also written 俄か【にわか】niwaka