Shellacking

To beat decisively
To coat with 'lac'

Examples:
... Schwartz helped the Titans defeat Pittsburgh, Baltimore, Cleveland and Cincinnati. Included in that run was a 31-14 late-December shellacking of the Steelers.

Busking

Performing (usually music) for free at public places, aiming to get tips. Like you would see being done at train stations etc.

At least in London 'Tube' I know that proper license if given for busking and the 'Tube' administration even recommends giving tips to buskers. And mostly I have found these artists to be talented enough to deserve some tips and respectful listening.

One interesting case, that I got to know recently is from New York, where a celebraty Violanist played as an incognito busker and got 32 dollars after performing about an hour. Teaches something about perceptiont and shows how much beauty we ignore while rushing through our rut race. Read on Pearls Before Breakfast.

Recce

Recce: Short form of reconnaissance, specially the verb form of reconnaissance.

Example
The police also revealed that one of those arrested had allegedly done a recce of one of Gandhi’s lawyers house in the Capital.
HT news about underworld shooters' arrest in New Delhi

Caterwaul

To wail like like a cat.
To fight like screeching cats, having noisy arguments etc

Example
As always, he caterwauled at the sheer size of the shocking verdict, and blamed it on the undue passion created by Baker's attorneys that inflamed the jurors.
The Appeal, by John Grisham

To take a rain check

Background: Suppose you bought costly ticket to a match and then it got canceled due to rain. To save you from the loss of money, the match organizer can give you ticket-stub along with the ticket- the stub can be used as ticket when the 'replacement match' is played.

So now, taking a rain check would mean opting to leave main opportunity but still keep the option of availing it in future.

Another meaning of the term is option given by companies to avail of their promotion (sale, free-gift etc.), when they run out of stock.

Examples
- Dinner at your place this weekend? I hope I can take a rain check.
- During the 2007 Christmas season, demand for Nintendo Wii was so strong that Nintendo was forced to issue rain checks to customers
from book Strategic Innovation: New Game Strategies for Competitive Advantage

Sow your wild oats

Read the term in Neil Strauss' The Game- "The pickup thing was never about sowing my wild oats". As one can understand from the worrding itself, it has something to do with 'spreading seeds' :).

Roughly speaking it means-
to have wild sex life,
to have sexual relations with multiple partners,
to have one's fling of affairs,

I think the wording itself makes it clear that the term is intended more for males. The term is mostly used for indicating a young male's fun-filled life, before he gets married.

There is exact idiom for this 'phenomenon' in French- "jeter sa gourme". Trying to dissect this one literally, one understands the meaning much more graphically.