1. Serving or intended to explain or make clear
   "explanatory notes"; "an explanatory paragraph"

See also: explain, informative, instructive

• Old Line State
• old maid
• old maid flower
• old man
• old man of the mountain
• old man's beard
• old master
• old money
• Old Nick
• Old Norse
• Old North French
• Old North State
• old person
• Old Prussian
• old rose
• old salt
• Old Saxon
• old school
• old school tie
• old sledge
• Old South
• old squaw
• old stager
• old style
• Old Style calendar