1. Lasting for a markedly brief time
   "rapid momentaneous association of things that meet and pass"
   - fleeting, fugitive, momentary

See also: moment, short

• protoctist family
• protoctist genus
• protoctist order
• Protoctista
• protogeometric
• protoheme
• protohemin
• protohippus
• protohistory
• protology
• protomammal
• protomartyr
• proton
• proton accelerator
• proton magnetic resonance
• protonotary
• protoplasm
• protoplasmic
• protoplasmic astrocyte
• protoplast
• protostar
• Prototheria
• prototherian
• prototypal
• prototype