Comorbid
Oxford defines this as: "denoting or relating to diseases or medical conditions that are simultaneously present in a patient." ASD is often comorbid with OCD, SPD, Epilepsy, Gastro Disorders, Anxiety, Depression, and BPD.

Dyspraxia
Dyspraxia, also known as developmental coordination disorder (DCD), is a developmental disorder that causes problems with movement, coordination, judgment, processing, memory, and some other cognitive skills. It can also affect the body’s immune and nervous systems. Dyspraxia is fairly common and a very frequent comorbidity of Autism.

Echolalia
Echolalia causes individuals to repeat noises, sounds or phrases that they hear. ASD individuals can often develop Echolalia with verbal stimming as a self regulation method. Echolalia is very different from Tourettes Syndrome, which causes a person to to suddenly say or yell random things suddenly as a part of a tic.

EDF
Executive functions are a broad group of skills that enable people to complete tasks and interact with others. An Executive Function Disorder (EFD) can impair a person's ability to organize themselves and control their behavior--these include ADHD and ADD, though someone can be given a broad diagnosis of EFD.

Infodumping
Also called monologuing, is when an individual with ASD talks at length, usually about an SI. This can often come with a lack of awareness of other parties interest via body language and subtle reactions. Keira Fulton-Lees has a great post about InfoDumping on Medium.

Masking
Masking is a complex and costly survival strategy for Autistic people. It generally involves intentionally learning neurotypical behaviors and mimicking them in social situations. Though often learned naturally from a young age, this behavior can be incredibly damaging to Autistic people as their lives go on.

Meltdown
If an individual with ASD becomes overwhelmed by stress or a situation, may result in a meltdown. Meltdowns are entirely out of the individuals control and are no caused by anger or a temper tantrum as some imply. This loss of control may manifest in verbal outbursts like shouting, screaming and crying; physical outbursts like kicking, lashing out, or biting; or both.

NT
Oxford defines Neurotypical (NT) as "not displaying or characterized by autistic or other neurologically atypical patternsof thought or behavior." NT is a term widely used in the ASD community as a label for someone without ASD or any other neurological or mental disorders.

OCD
Frequently misrepresented in media, Obsessive Compulsive Disorder is a disorder in which people have recurring, unwanted thoughts, ideas, or sensations (obsessions) that make them feel driven to do something repetitively (compulsions). This can range from worries about negative reactions from deviating from rigid routines to violent or otherwise unsavory intrusive thoughts or compulsions.

RSD
Rejection Sensitive Dysphoria (RSD) is a highly common symptom of EFD, specifically ADHD. This is generally a strong emotional reaction to perceived rejection, which can range from angry lashing out to outright panic. People who have the condition sometimes work hard to make everyone like and admire them, or they might stop trying and stay out of any situation where they might get hurt.

Shutdown
Inversely to a Meltdown which expresses and regulates emotions externally, a shutdown does so internally. Shutdowns are also caused by over stimulation or becoming overwhelmed. Shutdowns result in the individual going totally or mostly unresponsive. Just like Shutdowns, this is totally out of the individuals control.

Stim
Self-Stimulatory behavior consists of repetitive actions or movements meant to help self regulate emotion or help alleviate stress. Stimming comes in many forms. It can be physical like spinning in circles, "hand flapping," or rocking. Stimming can also be vocal, the individual may repeat a noise over and over simply because it is a pleasing noise. Most stimming behavior is natural and out of the persons control.

Special Interest
Individuals with ASD often take one or more Special Interests (SI). These SI often manifest in intense and passion interests in a subject. The individual may lose themself in the topic to the degree they forget to eat, handle responsibilities, sleep, or even not noticing physical pain and further damaging the body. While sometimes compared to an "intense nt hobby," SI's are often a requirement for individuals with ASD.

SPD
Sensory Processing Disorder (SPD), is a neurological condition in which sensory signals are not processed appropriately. SPD may manifest in extreme sensitivity to sunlight, as the brain perceives the sunlight, but processes the sensory input incorrectly. This results in the individual feeling more like a flashlight is being shone directly in their eye. Because SPD is neurological it can can even cause the individuals intense pain. SPD can also manifest with high aversions to specific food, textures, and fabrics.