what does it mean like undefined reference?

edit

straight dump of the console output:

srinaath@srinaath-desktop:~/catkin_ws3$ catkin_make
Base path: /home/srinaath/catkin_ws3
Source space: /home/srinaath/catkin_ws3/src
Build space: /home/srinaath/catkin_ws3/build
Devel space: /home/srinaath/catkin_ws3/devel
Install space: /home/srinaath/catkin_ws3/install
####
#### Running command: "make cmake_check_build_system" in "/home/srinaath/catkin_ws3/build"
####
-- Using CATKIN_DEVEL_PREFIX: /home/srinaath/catkin_ws3/devel
-- Using CMAKE_PREFIX_PATH: /opt/ros/melodic
-- This workspace overlays: /opt/ros/melodic
-- Found PythonInterp: /usr/bin/python2 (found suitable version "2.7.17", minimum required is "2") 
-- Using PYTHON_EXECUTABLE: /usr/bin/python2
-- Using Debian Python package layout
-- Using empy: /usr/bin/empy
-- Using CATKIN_ENABLE_TESTING: ON
-- Call enable_testing()
-- Using CATKIN_TEST_RESULTS_DIR: /home/srinaath/catkin_ws3/build/test_results
-- Found gtest sources under '/usr/src/googletest': gtests will be built
-- Found gmock sources under '/usr/src/googletest': gmock will be built
-- Found PythonInterp: /usr/bin/python2 (found version "2.7.17") 
-- Using Python nosetests: /usr/bin/nosetests-2.7
-- catkin 0.7.29
-- BUILD_SHARED_LIBS is on
-- BUILD_SHARED_LIBS is on
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- ~~  traversing 35 packages in topological order:
-- ~~  - geometry2 (metapackage)
-- ~~  - navigation (metapackage)
-- ~~  - openslam_gmapping
-- ~~  - slam_gmapping (metapackage)
-- ~~  - move_base_msgs
-- ~~  - tf2_msgs
-- ~~  - tf2
-- ~~  - tf2_bullet
-- ~~  - tf2_eigen
-- ~~  - map_server
-- ~~  - tf2_py
-- ~~  - map_msgs
-- ~~  - rplidar_ros
-- ~~  - tf2_ros
-- ~~  - tf2_geometry_msgs
-- ~~  - amcl
-- ~~  - fake_localization
-- ~~  - tf2_kdl
-- ~~  - test_tf2
-- ~~  - tf2_sensor_msgs
-- ~~  - tf2_tools
-- ~~  - nox_description
-- ~~  - voxel_grid
-- ~~  - costmap_2d
-- ~~  - nav_core
-- ~~  - base_local_planner
-- ~~  - carrot_planner
-- ~~  - clear_costmap_recovery
-- ~~  - dwa_local_planner
-- ~~  - move_slow_and_clear
-- ~~  - navfn
-- ~~  - global_planner
-- ~~  - rotate_recovery
-- ~~  - move_base
-- ~~  - nox
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- +++ processing catkin metapackage: 'geometry2'
-- ==> add_subdirectory(geometry2/geometry2)
-- +++ processing catkin metapackage: 'navigation'
-- ==> add_subdirectory(navigation/navigation)
-- +++ processing catkin package: 'openslam_gmapping'
-- ==> add_subdirectory(openslam_gmapping)
-- +++ processing catkin metapackage: 'slam_gmapping'
-- ==> add_subdirectory(slam_gmapping)
-- +++ processing catkin package: 'move_base_msgs'
-- ==> add_subdirectory(navigation_msgs/move_base_msgs)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Generating .msg files for action move_base_msgs/MoveBase /home/srinaath/catkin_ws3/src/navigation_msgs/move_base_msgs/action/MoveBase.action
-- move_base_msgs: 8 messages, 0 services
-- +++ processing catkin package: 'tf2_msgs'
-- ==> add_subdirectory(geometry2/tf2_msgs)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Boost version: 1.65.1
-- Found the following Boost libraries:
--   thread
--   chrono
--   system
--   date_time
--   atomic
-- Generating .msg files for action tf2_msgs/LookupTransform /home/srinaath/catkin_ws3/src/geometry2/tf2_msgs/action/LookupTransform.action
-- tf2_msgs: 9 messages, 1 services
-- +++ processing catkin package: 'tf2'
-- ==> add_subdirectory(geometry2/tf2)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Boost version: 1.65.1
-- Found the following Boost libraries:
--   system
--   thread
--   chrono
--   date_time
--   atomic
-- +++ processing catkin package: 'tf2_bullet'
-- ==> add_subdirectory(geometry2/tf2_bullet)
-- Checking for module 'bullet'
--   Found bullet, version 2.87
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- +++ processing catkin package: 'tf2_eigen'
-- ==> add_subdirectory(geometry2/tf2_eigen)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- +++ processing catkin package: 'map_server'
-- ==> add_subdirectory(navigation/map_server)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Boost version: 1.65.1
-- Found the following Boost libraries:
--   filesystem
--   system
-- +++ processing catkin package: 'tf2_py'
-- ==> add_subdirectory(geometry2/tf2_py)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- +++ processing catkin package: 'map_msgs'
-- ==> add_subdirectory(navigation_msgs/map_msgs)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- map_msgs: 4 messages, 6 services
-- +++ processing catkin package: 'rplidar_ros'
-- ==> add_subdirectory(rplidar_ros)
-- +++ processing catkin package: 'tf2_ros'
-- ==> add_subdirectory(geometry2/tf2_ros)
-- Using these message generators: gencpp;geneus;genlisp;gennodejs;genpy
-- Boost version: 1.65.1
-- Found the following Boost libraries:
--   thread
--   chrono ...