The poor sour look on co-workers faces (as if sucking a lemon) when something or someone has ruined their day. This condition is highly infectious and seems to be more common on Mondays but there is also a high incidence of Lemon Wednesdays especially in the cold dark days of winter.
After observing several employees with this condition, the manager will exclaim, "well it's official, today is Lemon Monday, feel free to express yourself accordingly".
A day generally created for the purpose of making people wish they were someone else. The day you realize you have 4 days of work ahead of you and that they won't be going by fast at all. Symptoms generally include feeling like crap, wishing you were dead, or not showing up for work in general.
A term used for a couple in the South-Korean variety show, "Running Man". The couple consists of two people, Gary (개리) and Song Ji Hyo (송지효). The two people are called Monday Couple as they only admit one another as their partner during Mondays only.