Concept that focuses on the components or elements of a structure or system and unifies them into a coherent and functional whole, according to a particular approach in achieving the objective(s) under the given constraints or limitations.
(According to: http://www.businessdictionary.com/definition/architectural-design.html)
Defining from a person's point of view:
Architectural design as problem solving by adding value. Breaking things down to their most simplistic state, we design things to solve problems. But it actually design does more than solving problems, it must also be helpful and beneficial to people.
(Taken and adapted from: http://bluearchitecture.wordpress.com/2011/06/18/what-is-architectural-design/)
Architecture design refers to the actual design and layout of spaces. Architecture encompasses many different elements including construction, design, and the manipulation of light as it relates to shadow. Throughout history, architects have found ways to create functional and practical spaces using any materials that were available.
This are my 3 Definitions for Architectural Design.