Popular techie words: we hear below words a lot in discussion & blogs. I thought it's good to have their definitions (easier ones) & explain if anyone asks "what's that?" as I also use them to have buzzwords compliance.

Technical Debt:
Technical Debt is a wonderful metaphor developed by Ward Cunningham to help us think about this problem. In this metaphor, doing things the quick and dirty way sets us up with a technical debt, which is similar to a financial debt. Like a financial debt, the technical debt incurs interest payments, which come in the form of the extra effort that we have to do in future development because of the quick and dirty design choice. We can choose to continue paying the interest, or we can pay down the principal by refactoring the quick and dirty design into the better design. Although it costs to pay down the principal, we gain by reduced interest payments in the future.
The metaphor also explains why it may be sensible to do the quick and dirty approach. Just as a business incurs some debt to take advantage of a market opportunity developers may incur technical debt to hit an important deadline. The all too common problem is that development organizations let their debt get out of control and spend most of their future development effort paying crippling interest payments.
Reference:
http://www.c2.com/cgi/wiki?TechnicalDebt
http://martinfowler.com/bliki/TechnicalDebt.html
http://www.youtube.com/watch?v=pqeJFYwnkjE

MapReduce:
MapReduce is hierarchical scatter/gather operation.
MapReduce is a library that lets you adopt a particular, stylized way of programming that's easy to split among a bunch of machines. The basic idea is that you divide the job into two parts: a Map, and a Reduce. Map basically takes the problem, splits it into sub-parts, and sends the sub-parts to different machines - so all the pieces run at the same time. Reduce takes the results from the sub-parts and combines them back together to get a single answer.
Reference:
http://scienceblogs.com/goodmath/2008/01/databases_are_hammers_mapreduc.php

Cloud Computing:
With cloud computing, everything is web-based instead of being desktop-based; access all programs and documents from any computer that’s connected to the Internet is possible. Cloud computing helps to do it more easily than ever before.

Wikipedia Cloud Computing is "a style of computing in which resources are provided as a service over the internet". Cloud computing user need not have worry about managing a machine or service at the physical level (Machine & location). Amazon Simple DB is an example for this as it handled operating system or database maintenance functions, SLA & operational issues.



Sharding:
Sharding or horizontal partitioning is about splitting up data sets. If data doesn't fit on one machine then split it up into pieces, each piece is called a shard.
Sharding is used when you have too much data to fit in one single relational database.

Reference:
http://highscalability.com/sharding-hibernate-way
http://highscalability.com/unorthodox-approach-database-design-coming-shard
http://lethargy.org/~jesus/archives/95-Partitioning-vs.-Federation-vs.-Sharding.html

Refactoring:
Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior. Its heart is a series of small behavior preserving transformations

Reference:
http://www.refactoring.com/
http://en.wikipedia.org/wiki/Code_refactoring

Code Smell:
In computer programming, code smell is any symptom in the source code of a program that possibly indicates a deeper problem.
Reference:
http://en.wikipedia.org/wiki/Code_smell