NT = Neurotypical (a mythical designation which is Autistic slang for Non-Autistic persons)
ASD = Autism Spectrum Disorder
HFA / LFA = High Functioning / Low Functioning Autistic (differentiating points along an imaginary 'spectrum' that includes both those who cannot care for themselves without physical assistance as well as those who are reasonably independent, but may require some external support to manage, and those who manage with no support at all.)
PDD-NOS = Pervasive Developmental Disorder - Not Otherwise Specified ('sort of Autistic, but doesn't fit enough criteria for a specific diagnosis of AS or HFA')
DX = diagnosis
Executive Dysfunction = an aspect of Autism, causing retardation of part of the frontal lobe that governs:
# behavior in situations that involve planning or decision making.
# behaviors in situations that involve error correction or troubleshooting. (processing-on-the-fly)
# behaviors in situations where responses are not well-learned or contain novel sequences of actions.
# reactions to dangerous or technically difficult situations.
this part of brain function is commonly known as The Executive Function
Stims or Stimming = 'self stimulating behaviors', i.e, rocking, swaying, hand-flapping, etc. - Movements that help disperse chronic anxiety, due to hypersensitivity to stimuli.
There are a few other abbreviations you'll see here that involve programs for schoolchildren, but i don't recall those offhand...