Isn't Dick's definition unnecessarily restrictive, i.e. 14 rhymed pentameters with (usually) a turn? Here are two tet sonnets (?), one of which turns at line 9, the other at line 7.

The Aerie

Hand-laid cables of braided twine
anchored a Boy Scout monkey bridge.
Over it rose an aspen ridge
where ospreys hunched on a blasted pine.

Ever a student of their flight,
I’ve envied them the breakneck plunge,
the snatched fish and the skyward lunge
from Bad Axe Lake to Key West Bight.

An osprey perched on the foremast
of a tall schooner berthed near mine
watches me cinch a slack springline.
So the familiars of my past
accepted an ungainly guest
and fledged a sailor from their nest.

The Visitant
for Suzanne Doyle

When last this comet crossed the West
Sappho lay on her lover’s breast.
How I’d have loved to hear her speak
its praises in Aeolic Greek,
mankind’s most majestic tongue
for which Apollo’s lyre was strung.
When next this astral visitant
returns from its celestial jaunt,
will jewels in Berenice’s Hair
still shine above a planet where
lovers observe a comet’s flight
then light a votive lamp to write
strophes a poet might have sung
when Sappho and the Gods were young?

It seems to me that testing the rules of the sonnet is almost part of the tradition of the sonnet in English (otherwise we'd only have Petrarchan sonnets for one)--and there is practically a whole separate genre of nonce-rimed sonnets, and plenty of sonnets in other meters, as this Shakespeare tet. sonnet (not one of his best though--assuming it is indeed his):

CXLV

Those lips that Love's own hand did make,
Breathed forth the sound that said 'I hate',
To me that languished for her sake:
But when she saw my woeful state,
Straight in her heart did mercy come,
Chiding that tongue that ever sweet
Was used in giving gentle doom;
And taught it thus anew to greet;
'I hate' she altered with an end,
That followed it as gentle day,
Doth follow night, who like a fiend
From heaven to hell is flown away.
'I hate', from hate away she threw,
And saved my life, saying 'not you'.


Dick's guidelines describe the norm, of course. And it wouldn't be much fun to play with the rules if the rules weren't so well established in the first place.

I agree wholly with AEStallings - there is a norm and there are variations from the norm. When the variations get further and further away we tend to be uncomfortable using the word "sonnet", and each of us will probably draw that line in a slightly different place. The word sonnet in English orginally meant little song, and was not even tied to 14 lines, of any length. I don't think it really matters how we label these poems, whether we call them sonnets or not (as with Meredith's 16 line "sonnets"): obviously that's formally where they start from, but they have gone off in their own direction. They're nice poems, and that surely is what matters, rather than labels.
Something perhaps only partially relevant: the sonnet tends (only tends) to be assciated with fairly elevated diction in English, and the tone that produces is in turn associated with the pentameter. A tetrameter sonnet breaks that connection (I'm not saying that's good or bad, just pointing it out). But of course from the romantic period onward we get all sorts of diction in sonnets - down to the very homely indeed (as in John Clare's sonnets). The form gets constanty extended, including more sorts of experience, more sorts of diction, and technical variations..