What does PMMA stand for?

Polymethyl methacrylate (PMMA) or poly (methyl 2-methylpropanoate) is the synthetic polymer of methyl methacrylate. This thermoplastic and transparent plastic is sold by the tradenames Plexiglas, Limacryl, R-Cast, Perspex, Plazcryl, Acrylex, Acrylite, Acrylplast, Altuglas, Polycast and Lucite and is commonly called acrylic glass or simply acrylic. The material was developed in 1928 in various laboratories and was brought to market in 1933 by Rohm and Haas Company.

The material is often used as an alternative to glass. Differences in the properties of the two materials include

PMMA is less dense; its density can range from 1150-1190 kg/m3. This is less than half the density of glass which ranges 2400 to 2800 kg/m3.
PMMA has a higher impact strength than glass and does not shatter but instead breaks into large dull pieces.
PMMA is softer and more easily scratched than glass. This can be overcome with scratch-resistant coatings.
PMMA is typically processed at a lower temperature than glass, just 240-250 °C.
PMMA transmits more light (up to 93% of visible light) than conventional glass. However, there exist special optical grades of glass that can transmit up to 98% of light.
Unlike glass, PMMA does not filter ultraviolet (UV) light. PMMA transmits UV light down to 300 nm. Some manufacturers add a coating to PMMA sheets to make them absorb UV light. PMMA molecules have great UV stability compared to polycarbonate.
PMMA allows infrared light of up to 2800 nm wavelength to pass. IR of longer wavelengths, up to 25,000 nm, are essentially blocked. Special formulations of colored

PMMA or Acrylic is a versatile material and has been used in a wide range of fields and applications.

Impact resistant substitute for glass
PMMA Acrylic glass is commonly used for constructing residential and commercial aquariums.
PMMA is used in the lenses of exterior lights of automobiles.
The spectator protection in ice hockey stadiums is made of PMMA.
Motorcycle helmet visors
Police vehicles for riot control often have the regular glass replaced with acrylic to protect the occupants from thrown objects.
Lucite was used for windows on the Bathyscaphe Trieste which descended to the lowest point on the ocean floor, the Challenger Deep.
Polycast acrylic sheet is the most widely used material in aircraft transparencies (windows). In applications where the aircraft is pressurized, stretched acrylic is used.

Medical technologies and implants
PMMA has a good degree of compatibility with human tissue, and can be used for replacement intraocular lenses in the eye when the original lens has been removed in the treatment of cataracts. Hard contact lenses are frequently made of this material. Soft contact lenses are often made of a related polymer, where acrylate monomers containing one or more hydroxyl groups make them hydrophilic.
In orthopaedics, PMMA bone cement is used to affix implants and to remodel lost bone. It is supplied as a powder with liquid methyl methacrylate (MMA). When mixed these yield a dough-like cement that gradually hardens. Surgeons can judge the curing of the PMMA bone cement by pressing their thumb on it. Although PMMA is biologically compatible, MMA is considered to be an irritant and a possible carcinogen. PMMA has also been linked to cardiopulmonary events in the operating room due to hypotension. Bone cement acts like a grout and not so much like a glue in arthroplasty. Although sticky, it primarily fills the spaces between the prosthesis and the bone preventing motion. It has a Young's modulus between cancellous bone and cortical bone. Thus it is a load sharing entity in the body not causing bone resorption.
Dentures are often made of PMMA, and can be colour-matched to the patient's teeth. In cosmetic surgery, tiny PMMA microspheres suspended in some biological fluid are injected under the skin to reduce wrinkles or scars permanently.

I hope this can help your understanding. =)