He’s a good ten years younger than her.
She’s been waiting for a good hours.
What do the words in italics mean?
Thanks.it means “at least this much”
dictionary.cambridge.org/us/dict … ish/a-good
“a good hours” does not make sense though - maybe you mean “a good hour”
Or maybe
She’s been waiting for a good few hours.
a good few = several
To me, here, ‘a good’ would mean ‘pretty long’.
For me ‘a good + amount/quantity’ suggests probably more than that amount/quantity
Yes, both of you are right, I omitted ‘two’ in the phrase, in fact, it shoud read as:
She’s has been waiting for a good two hours. 
Thanks
To clear up the meaning regarding ‘a good’, that would indicate she’s been waiting for a full two hours plus some additional time.
Similarly, a good ten years younger, would indicate that he is a full 10 years younger, plus extra months.
As Alan said… “more than the stated quantity”.