1. Difficult to place in an adoptive home

Antonym: adoptable

• locking pliers
• lockjaw
• lockkeeper
• lockman
• lockmaster
• locknut
• lockout
• lockram
• lockring
• locksmith
• lockstep
• lockstitch
• lockup
• locky
• loco
• loco disease
• locoism
• locomote
• locomotion
• locomotive
• locomotive engine
• locomotive engineer
• locomotor
• locomotor ataxia
• locoweed