1. to not feel attractive or happy all day because you cannot make your hair look nice.

I'm having a bad hair day today - I just couldn't do a thing with it this morning. (humorous)

2. if a machine has a bad hair day, it does not work as it should all day.

My computer's having a bad hair day.

• hard nut
• hard nut to crack
• hard-on
• hard on heels
• hard on someone's heels
• hard on the heels of
• hard on the heels of something
• hard put to
• hard put to do something
• hard row to hoe
• hard sell
• hard stuff
• hard to swallow
• hard to take
• hark back to
• hark back to something
• harm a hair on head
• harm a hair on someone's head
• harp on
• harp on something
• has-been
• has got game
• hash out
• hash out something
• has more bark than bite