aer·om·e·ter 
(â-rŏmĭ-tər)
(â-rŏmĭ-tər)n.
An instrument for determining the weight and density of air or another gas.
- obsession
- obsessional
- obsessionally
- obsessive
- obsessive-compulsive
- obsessive-compulsive disorder
- obsessive-compulsive personality disorder
- obsessively
- obsessiveness
- obsessor
- obsidian
- obsolesce
- obsolescence
- obsolescent
- obsolescently
- obsolete
- obsoletely
- obsoleteness
- obsoletism
- obstacle
- obstacle course
- obstetric
- obstetrical
- obstetrically
- obstetrician