undef_method.rb

puts '====='

puts 'defining the Parent class with #poop'
class Parent
  def poop
    puts "💩 💩"
  end
end

puts 'defining the Child < Parent class with #poop'
class Child < Parent
  def poop
    puts "💩 "
  end
end

puts 'defining the Baby < Child class with #poop'
class Baby < Child
  def poop
    puts "💩 "
  end
end

puts 'creating instances of each class'
child = Child.new
parent = Parent.new
baby = Baby.new

puts 'sending #poop to each class'
parent.poop
child.poop
baby.poop

puts '---'

puts "parent.respond_to?(:poop) -> #{parent.respond_to?(:poop)}"
puts "child.respond_to?(:poop) -> #{child.respond_to?(:poop)}"
puts "baby.respond_to?(:poop) -> #{baby.respond_to?(:poop)}"

puts 'opening baby to remove_method(:poop)'
class Baby
  remove_method(:poop)
end

puts "parent.respond_to?(:poop) -> #{parent.respond_to?(:poop)}"
puts "child.respond_to?(:poop) -> #{child.respond_to?(:poop)}"
puts "baby.respond_to?(:poop) -> #{baby.respond_to?(:poop)}"

puts 'opening child to undef_method(:poop)'
class Child
  undef_method(:poop)
end

puts "parent.respond_to?(:poop) -> #{parent.respond_to?(:poop)}"
puts "child.respond_to?(:poop) -> #{child.respond_to?(:poop)}"
puts "baby.respond_to?(:poop) -> #{baby.respond_to?(:poop)}"

http://ruby-doc.org/core-1.9.3/Module.html#method-i-undef_method