context.rb

class A
  Const = lambda{ p [ :in_lambda, self, @foo ] }

  define_method(:meth) do
    p [:in_method, self, @foo]
    Const.call
  end

  def initialize
    @foo = 72
  end
end

A.new.meth
# Result:
# => [:in_method, #<A:0x007f8f690117d8 @foo=72>, 72]
# => [:in_lambda, A, nil]

define_method_with_lambda.rb

class A
  Const = lambda{ p [ :in_lambda, self, @foo ] }

  define_method(:method_from_lambda, &Const)

  def initialize
    @foo = 72
  end
end

A.new.method_from_lambda
# => [:in_lambda, #<A:0x007f8f69011468 @foo=72>, 72]