Made-to-measure

Made-to-measure (MTM) typically refers to custom clothing that is cut and sewn using a standard-sized base pattern. Suits and sport coats are the most common garments made-to-measure. The fit of a made-to-measure garment is expected to be superior to that of a ready-to-wear garment because made-to-measure garments are constructed to fit each customer individually based on a few body measurements to customize the pre-existing pattern. 
Made-to-measure garments always involve some form of standardization in the pattern and manufacturing, whereas bespoke tailoring is entirely made from scratch based on a customer's specifications with far more attention to minute fit details and using multiple fittings during the construction process. 
All else being equal, a made-to-measure garment will be more expensive than a ready-to-wear garment but cheaper than a bespoke one. "Custom made" most often refers to MTM.
Overview.
To order a made-to-measure garment, the customer's measurements are first taken by a made-to-measure retailer. Then a base pattern is selected that most closely corresponds with the customer’s measurements. This base pattern is altered to match the customer’s measurements. The garment is constructed from this altered pattern.
The primary benefits to the customer of made-to-measure clothing are that the garments will be well-fitted to the customer's body and the customer may have the opportunity to customize the fabric and detailing. The primary disadvantage of made-to-measure is that the customer must wait up to several weeks for the garment to be sewn and delivered. A typical price markup for a made-to-measure item is 15% over the price of its ready-to-wear counterpart.
Made-to-measure retailers often travel internationally meeting clients in cities, providing samples of the latest materials and styles.
Unlike bespoke garments, which traditionally involves hand sewing, made-to-measure manufacturers use both machine- and hand-sewing. Made-to-measure also requires fewer fittings than bespoke, resulting in a shorter wait between customer measurement and garment delivery.
Made-to-measure is sometimes also referred to as personal tailoring.
In recent years tailoring has evolved further with young companies like Artefact London, that make a blend of made-to-measure and bespoke approaches. A base pattern is used to gauge your measurements and your unique pattern is created electronically with all alterations accounted for prior to cutting. Thus alleviating the need for baste fitting that is mandatory in bespoke with very minor alterations (if any) needed at the fitting.
Advertising Standards Authority ruling.
In the United Kingdom, the legal definition of “made-to-measure” has been conflated with bespoke tailoring by a ruling of the Advertising Standards Authority. The ruling is based on the Oxford English Dictionary definition of bespoke as "made to order". While this ruling clarified the difference between bespoke and ready-to-wear, it had the effect of blurring the line between bespoke and made-to-measure.
The ruling established that a "made-to-measure suit would be cut, usually by machine, from an existing pattern, and adjusted according to the customer's measurements," while "a bespoke suit would be fully hand-made and the pattern cut from scratch, with an intermediary baste stage which involved a first fitting so that adjustments could be made to a half-made suit." The ruling concluded, however, that a "majority of people... would not expect that bespoke suit to be fully hand-made with the pattern cut from scratch," effectively equalizing the terms bespoke and made-to-measure.
While etymologist Michael Quinion observed that by definition "it was legitimate for a tailor offering clothes cut and sewn by machine to refer to them as bespoke, provided that they were made to the customer's measurements", since the traditional use of bespoke inside the tailoring community has been more nuanced than the Oxford definition, others concluded that the ASA "took a rather ignorant decision to declare that there is no difference between bespoke and made-to-measure."