gistfile1.rb

class Foo
  def define(name, &block)
    class << self; self; end.send(:define_method, name, block)
  end

  def define2(name, &block)
    define(name, &block)
  end

  def test
    define(:foo) { return 1 }
    call_foo
    puts :here
  end

  def call_foo
    foo
  end
end

Foo.new.test