1. (of rules) stringently enforced
   "hard-and-fast rules"
   - strict

See also: invariable

• flanker back
• flannel
• flannel leaf
• flannel mullein
• flannel-cake
• flannelbush
• flannelette
• Flannery O'Connor
• flap
• flap down
• flapcake
• flapdoodle
• flapjack
• flapper
• flapping
• flaps
• flare
• flare out
• flare pass
• flare path
• flare star
• flare-up
• flaring
• flash
• flash butt welding