used to refer to something which is boring or without meaningful content

the first 20 pages are a lot of blah about budgets and stuff like that

depression

a case of the blahs

dull or unexciting

the game has been very blah

used to substitute for actual words in contexts where they are felt to be too tedious or lengthy to give in full

he said nations great and small could come together to blah blah blah