He plans to 'thin' (out) the young carrots in the garden. [=to remove some of them so that there is more room between the remaining carrots]
His hair is a little 'thin' on top. = He's a little 'thin' on top. [=he does not have a lot of hair on the top of his head]
The bank's decision to raise rates could be 'the thin end of the wedge'. [=many other banks may also decide to raise rates]
(..) Yeah? And do you know Martha Pigot? Yes. Really? What's she look like? What do you mean? Blonde, brunette, tall,shortish, thin, fat? What's she look like? Blind. Blonde or brunette? Quickly. Brunette! Damn it, that's enough! There's no problem! (..)1981 To Kill a Cop