under_the_weather
1. [ adjective ] somewhat ill or prone to illness
Synonyms: ailing peaked poorly sickly unwell indisposed
Examples:

"my poor ailing grandmother" "feeling a bit indisposed today" "you look a little peaked" "feeling poorly" "a sickly child" "is unwell and can't come to work"

Related terms: ill
Similar spelling:   under_the_thumb_of
  under-the-table