Tad bit means a little amount of something and is synonymous with tidbit and titbit. Though it is always spelled as two words. Tad and bit can both be used on their own for a similar meaning. The use of both may seem redundant, however, it is an accepted phrase. It should not be used with another size adjective (e.g., a little tad bit or tad bit little).
All terms are usually used with the article a.
The phrase a bit can also signify a small amount of time or distance.
Be aware that bit on its own has alternative meanings such as the piece of a horse’s reins that goes in the horse’s mouth, a piece of a drill that bores into material, part of binary code, the past tense of bite, and a comedy routine.
Examples
It was a tad bit ironic that since Royal Belum is home to numerous birds and mammals, sightings of living things (other than fellow human beings) were scarce. [Malaysian Insider]
It will be a tad bit humid this weekend but our overall comfort level will be pleasant. [FOX 59]
The Dubai index ended a tad lower on Thursday led by Emaar as investors booked profits ahead of holidays. [Gulf News]
The very affordable Dacia Duster has been given a bit of a makeover for the UK for 2015 with cosmetic tweaks and quality improvements. [CarsUK]
We’ll get to some fun baseball player conversations on this topic in a bit, including a chat with, arguably, the most educated player currently in MLB. [Fox Sports]