[Xelebes]

Personal definition:

Single-floor
Two-floor

Low-rise (3-4 stories)
Midrise (5-9 stories)
Highrise (10-18 stories, higher if the width of the building is larger than the height.)

Tower (More than 5 stories, but the height has to be more than the width.)

Small Skyscraper (19-30 stories or about 60-100 m, but if and only if the structure is amongst the tallest buildings in the settlement - like that in the skyline of Saskatoon or Yellowknife.)
Moderate Skyscraper (30-45 stories or about 100-150 m)
Medium Skyscraper (45-70 stories or about 150-240 m)
Tall Skyscraper (70-90 stories or about 240-300 m)
Supertall Skyscraper (90-150 stories or about 300-500 m)
Megatall Skyscraper (500-1000 m)
Hypertall Skyscraper (1000+ m)