Meaning of 'To plumb the depths of hell and meet'

[Tamara]

Hi

I understand the direct meaning of plumb (and some indirect ones that implied by it ).
But some specific phrases still confuse me (and , maybe, my dictionary isn't perfect...)

Like:
plumb against me – OK, that's more or less logical…

but:
perfectly plumb
plumb dullness
I plumb forgot

Can you help me 'to join' direct and indirect meanings of that plumb for such cases?

Does it just like square (used in its indirect meaning, as well)?
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It’s impossible to learn swimming without entering the water…

[Mister Micawber]

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I am not clear on what you are looking for, Tamara. The American Heritage Dictionary (for instance) includes all the definitions relevant to your listed examples:

ADVERB: 1. In a vertical or perpendicular line. 2. Informal Directly; squarely: 'fell plumb in the middle of the puddle'. 3. also Informal Utterly; completely: 'plumb worn out'.

ADJECTIVE: 1. Exactly vertical. 2. also Informal Utter; absolute; sheer: 'a plumb fool'

NOTE: A connection between concrete and metaphorical meaning lies behind the Southern adverbial usage of plumb, as in 'He fell plumb asleep' as an indicator of completeness or totality. .

When you feel that your dictionary is inadequate, may I suggest that you try ONE LOOK DICTIONARY SEARCH?
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Native English teacher at Mister Micawber's

[Tamara]

Thank you, Mister Micawber!

Since yesterday I've found out several good definitions, but with no doubt I'll examine your links carefully

P.S.
By the way (just one point): what you would call as plumb belly in Russian is flat belly.
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It’s impossible to learn swimming without entering the water…

[Mister Micawber]

.
Sorry, I've never heard 'plumb belly', but I've got a nice flat stomach-- I've been working seriously on my abs.

(Ms Google hasn't much, either: only 7 English pages for "plumb belly"!)
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Native English teacher at Mister Micawber's

[Tamara]

[Conchita]

We can safely assume that MM has a six-pack (stomach), then (or is on the road to getting one). I like the Spanish expression, too: a chocolate bar or (for the severely muscled ) a toblerone!