have (something) up (your) sleeve

to have a secret idea or plan.

If this trip doesn't work out I've still got a few ideas up my sleeve.

• hide head in the sand
• hide light under a bushel
• hide your head in the sand
• hide your light under a bushel
• high and mighty
• highest rung on the ladder
• high-flier
• high ground
• high jinks
• highly-strung
• high roller
• highways and byways
• hinge on
• hinge on something
• history in the making
• hit a brick wall
• hit a home run
• hit and miss
• hit a nerve
• hit a raw nerve
• hit a snag
• hit a wall
• hit back
• hit below the belt
• hit between the eyes