1. Adverb (fukushi), Adverb taking the 'to' particle, Suru verb

   tightly (holding on); firmly; securely

   Usually written using kana aloneOnomatopoeic or mimetic word

   君にはもっとしっかり仕事をしてもらいたい。

2. strongly (built); solidly; sturdily; steadily

   Usually written using kana aloneOnomatopoeic or mimetic word

3. properly; well; sufficiently; hard (working, etc.); fully; completely

   Usually written using kana aloneOnomatopoeic or mimetic word

4. reliably; dependably; levelheadedly; shrewdly; wisely; cleverly

   Usually written using kana aloneOnomatopoeic or mimetic word

Also written 聢り【しっかり】shikkari